What approach to take?

I shouldn't think it would be as easy as you assume janeainsworth when someone's refused to talk to you for 9 months.

Ignoring the 'elephant in the room' is never easy especially a the OP's son knows what the problem is and refuses to discuss it with his parents, therefore denying them the opportunity to try and sort things out.

Like you, I'd be unhappy if that had ever happened to me. That said I wouldn't have been surprised if I'd refused to speak to her for 9 months and made my reluctance for her to stay obvious.

smileless Perhaps you don’t believe in burying the hatchet, or least said, soonest mended.
Personally I don’t like confrontation and ‘having things out’ - I think that far from ‘clearing the air’, it often simply makes things worse.
I prefer to forgive and forget.
But we are all different, I suppose.

Yes but what is she to forgive ? and who is to forgive ?

Oh dear.

I am sorry if I appear critical of DS here, but he is actually perpetuating the problem by refusing to be open with you.

He knows why his wife is unhappy, and knows that YOU know she is unhappy, but appears to push you together when this is clearly not working.

Without being mean, this sounds like a recipe for a rubbish Christmas for everyone.

DS should have the kindness to everyone involved to be honest about what the problem is. Acting like nothing is wrong is only going to make things worse.

Would it not be better to stay in a rented place than in the home of someone who clearly - for reasons DS refuses to disclose - does not want you there? The granddaughters will pick up that mummy is unhappy about your visit.

Was the money for the improvements given under the condition that you would stay regularly in the home, or was this something that only came to light later? What expectations did you have when you discussed the gift of the money with DS and was DIL aware of this?

I do not wish to project at all here, but my DH has accepted gifts of money from my MIL that came with particular expectations, not told me about either the source of the money or her expectations, and it has never failed to cause trouble all round.

I think before you embark on a potentially very difficult visit, DS owes you an explanation of what the issue is so that you can consider how to solve it.

The last sentence of your second post jarred with me.
Do you think that the gift of money for work on their house and your expectations from the gift could be the problem?
Not that I think you should stay in a B&B or similar as some posters suggested but you did sound as if you thought you were entitled to stay in their home because your gift money had been spent on their property.
This is how it came across to me and if you have shown any of this attitude to her, I don't think that it would go down very well.
You must realise that your Dil holds all the aces, so to speak.
They might be your adored Dgc but they are her children and he may be your Ds but he is her husband.
As you say he is trying desperately to pacify both you and her but you must realise that if there ever became a choice he would choose her.
I would tread very carefully!

I would stay nearby, simply because I couldn't stand to be manipulated: pushed away one minute, under their roof the next.
Neutral ground means you can come and go easier.

I think it would be simply ghastly to stay at that time of year with a strange atmosphere hanging about.

I would thank her very much for the invitation and say you just wanted to kindly ask if all was well and had you caused offence.

Just to clarify, I was not suggesting that the OP should stay in an hotel, but that she offers the DIL the option for her to do so. Essentially, if played correctly, you are setting out well in advance that the olive branch invitation has been accepted in the right spirit, and wantthatmake clear that you are taking the "their house, their way" approach.
Of course you hope that she will reply with confirmation that the invitation obviously does mean staying with them!

A quick google shows 4 flights a day into Luton from Geneva, and that was just checking one airline, so I would politely suggest that there is room to ask what times work for them.
As another poster mentioned, you catch more flies with honey than with vinegar!

Not knowing how big the house is, it is difficult to know whether an offer to stay in a hotel would cause further upset.

We always stay with DDiL's mother when we visit our DGC because their house is small. If it is not convenient to stay with her we book a B&B. If they had a large 4 bedroomed house, it would be different.

I would also opt to stay in an hotel if you can do so without causing offence. I suspect your DIL would be secretly relieved. That way you have somewhere to retreat to and you each have your own space. 4 days is a long time to spend together over the festive season even when there are no underlying tensions.

Whatever caused the original rift, and whatever the rights and wrongs of the situation, this is a massive olive branch and an opportunity to try to repair the relationship and see your grandchildren. Be as sensitive and kind as you can and try very hard not to let any underlying resentment show.

Like previous posters, I also wonder if your gift of money for the home improvements is a factor, either directly indirectly.

Your DIL sounds like a difficult person, maybe as a result of her relationship with her own mother, it probably doesn't do to speculate, but smile and think positive thoughts - you will be with your son and beloved grandchildren at Christmas.

Absolutely agree with Grans urging you to accept the invitation. You will regret it if you don't go; it's an olive branch although you may think it a small one. ChaosInc's suggestion of giving your dil the opportunity to suggest a local hotel, BnB or AirBnB is a good one so that your dil has the choice in case she had felt obligated to have you stay in the house. Sometimes it can be less wearing for all parties if the charm offensive doesn't have to be 24 hours a day and there is some opportunity for time out. Christmas is a notoriously difficult time for family relationship tensions so make it as easy as possible for everyone probably including some tired and over excited grandchildren.

4 days is a long time and I definitely would not feel comfortable staying with the family unless I felt wholly welcome and wanted. I would need a bolt-hole and would book somewhere to stay nearby. You could tell your son and DIL that you'd love to join the family over the festive season but think it'll be easier all round if you stay at an hotel.
Then I'd follow the advice of other Grans and be as nice as pie which would be easy knowing that there's a bolt-hole to retreat to if the going got tough. Good luck .

Oh go and act as if nothing has ever happened perhaps your daughter in law feels worried or ashamed that you’ve paid for so much, perhaps she didn’t want to be beholden to you maybe that’s what IT is who knows
Id be upset if my family stayed in hotels unless there was no room in my house
Go enjoy the grandkids, be pleasant to the daughter in law if it’s not returned, don’t worry it’s only a few days

I am with * buffy* & janea here! DS has probably negotiated this with his DW. It is an olive brach. Be bigger and stronger by accepting it with good grace. Say how fab the house looks..DO NOT MENTION THE -war- MONEY... It was,a,gift and is not anything to do with you how it is spent nor buys any special status! You could say thank you we 'd love to come and stay with you. Can you book a local place for dinner / lunch for us all one day..we would like to say thank you for accommodating us.

I find it very odd that your DS hasn’t told you what “it” is, how can anything be resolved, explained or apologised for if you do not know what you are dealing with. Surely he wants peaceful and healthy family relationships ? As others have said tho, your granddaughter is the most important thing here ... good luck.

We live in a different country to our DD and family and in the past found it more comfortable to stay in a hotel within walking distance. We ate all our meals and spent all our days with the family, but a bit of space is good for everyone especially at fraught times like xmas.

In your situation I would talk to DS say how you look forward to seeing them all, and would it help if you slepted in a hotel. It is then up to your son and DIL to decide.

Whatever your DILs problem is, I have found that time is a better healer than confrontation if you value family harmony, and if she struggles with relationships giving her some space whilst enjoying your time with GC and son may help build a bridge.

I'd be inclined to find out what the problem was first before having to endure 4 days of tension------which is no good for anyone's health. The atmosphere could be really strained and children can also pick up that all isn't as it should be too.
I'd definitely go once there's been a resolution.

An Airbnb 'locally' might allow you distance, independence and somewhere to see children outside their own home yet not in a public place. You can cook. You can invite them all for a meal!
Have used them often and never had a duff one yet.

I would go just to be with my gc and just be my normal cheerful self, include her in any chit chat but ignore it when she doesn't reply or talk back. Hopefully jour says will be so busy with our gc and son that you won't notice her not talking to you much.

Evianers, that is such a difficult situation. If you don't go, it might be seen as you're not interested in Gc. If you do go I think you will feel extremely uncomfortable. Would there be any way of a compromise where you go but either stay somewhere else and just spend a few hours each day with them. Or just go for a day, even if it is a long way. You could stay somewhere else and it would put a lot less pressure on you and dil.
CrazyH I'm glad I'm not the only one, got exactly the same retort.

Mmm, you point out that you have given a substantial sum for improvements to their home, then point out that you do not want to stay elsewhere. Could it be that your dil now thinks that you feel you have bought the right to stay in their house because of the money given? By making that remark on here it makes me wonder if you do think you have some rights over staying?
It would make my blood boil if my mil and fil had given me any money (they never did) then felt they somehow had a right over my home. Think back to see if either you or dh have made any comments about the money, whether in jest or not.

Well said to BUFFY! which makes perfect sense to me. Just be 'yourself' .... That's all we can be.

I prefer not to stay with anyone now and always book a hotel. Makes it more relaxing for everyone and I like an escape route.

I wouldn't confront DIL on anything. She's not talking ....
Fine! Just be yourself and make a conscious effort to have fun x

Just go and get on with it.

I'd stay in an hotel, bnb or airbnb, just to allow them to have some private time. I'd hate to hear arguments between husband and wife, even if they were in another room or even in bed.
Besides that aspect, a frosty atmosphere can put a dampener on the most joyous occasion and 4 days is a long time to spend under the same roof as a silent DiL.
At least, in an hotel, you can go to bed when you please and aren't 'having to be entertained' 24/7.

Be kind, thoughtful and interested in the family activities. Behave as if nothing is wrong and coast over any odd problems. If you expect to have no trouble and give none you will probably be welcomed - they must have wanted you to invite you - and you do not know what has really gone on. If you seem to think all is well it probably will be, so don't ask, she will tell you if she wants to but she may just want o sweep it under the carpet / let it drift into the past, especially if she has done some thinking and realised that she has got the wrong end of the stick somehow and is embarrassed to have misread a situation.

Good luck.