My grandchildren never thank me for anything I do for them.

Sounds a bit partisan.
Why do you assume their mother is at fault, they have two parents.
It is as much their father's responsibility to teach them manners and to consider others.

Hello Katiegrandma. Only seeing your GC once a year will make it extremely difficult for you to have that grandmother/grand child relationship, and if you never receive any thanks from mum, it's probably unlikely that she's told the children the importance of showing appreciation for gifts received.

There's also the possibility that they're not aware of the extent of your contribution to their music lessons and school trips.

From what you've posted, it doesn't look as if your son is in a position to do anything about this so I think you're right not to involve him.

Take some time to decide whether or not you wish to continue with the amount of financial assistance you're currently giving because if you're not getting any pleasure from doing so, now maybe the time to pull back a little .

Pull back a little indeed! You are not a minor Grandmother and you deserve some thanks . No thanks - no cash - !!

Depends, whether you do it to get pleasure or thanks, or to help their education.

The children live with their mother . I too would expect her to be mostly responsible for the upbringing of the children, which includes teaching them ‘manners’. I don’t think the OP being ‘partisan’.

is being ‘partisan’

I agree crazy the OP's explained her son's difficult relationship with the children's mother who clearly has the major parenting role.

Does your son thank you for what you are doing for his kids?

I understand where this grandmother is coming from, and I don’t think she’s being partisan, and even if she was partisan, why shouldn’t she be? It’s her son and assuming he has never abused his ex wife or children (and there seems to be no reason at all to suggest he has) then both the father and grandmother are being treated very shabbily by the mother. Why is grandma only allowed to see her grandchildren once a year? They all live in this country apparently. Visits are short because of the demands of their mother.

I have quite a lot of experience with difficult ex in laws, in my case an abusive ex son in law. My daughter and her children live abroad, although my daughter wants to come home with the children, but is unable to do so at this time. It’s a long story, and a difficult and complicated situation, which I cannot explain here, but it does give me some insight into these kinds of difficult people and situations. Of course this grandma should support her son, and she certainly should be partisan. The ex DiL is behaving badly towards her son and towards her. Sadly this is often the case after divorce. The children are used by the controlling partner, in this case, the mother, to punish and manipulate their ex partner. It’s sad, but believe me, it happens.

What a difficult situation for you OP. My first knee jerk reaction was to say stop giving anything. But on reflection that's not fair on the grandchildren who I expect you love. You may well be able to afford to spend freely. Many GNs are wealthy. But if you are going short yourself maybe cut down what you spend on them if it makes you feel a little less hard done by. Of course they should be thanking you or just keeping in touch with you. And you should see them more often. But life doesn't seem to work out like that for separated/divorced families. Don't worry about the other grandparents. Their situation is different and comparison is just upsetting.
Can you try and get a moment to discuss this with your son? With no recriminations. Just a discussion of how you want to go forward especially as Christmas is on the horizon. Maybe just a book token and a card. Buying books is tricky for teenagers I should think. Keep with the music lessons for the time being. How do you pay for them. Invoice? Or bank transfer to the teacher? Or money to DIL? Does your son confirm they are still having them knowing how fickle children can be.
I am sorry you are sad about this. It must be very difficult. I have no granchildren...just a grand dog. And he is eternally grateful for anything!

I think I would keep on with the gifts, at least until the children reach 18, if you can afford it.
Without knowing all the facts, Surely your son has regular access to his children, so why can’t you see them all together more often?

Maybe I’m missing something here, but doesn’t your son have his children on his own? If he does then surely a quick phone call or FaceTime when they can say thank you is possible?

May I say that by paying for their music lessons you are doing so much to improve their lives and helping their development.
Please don't stop that. Yes checking up that that is what the money is spent on is probably a good idea.
Showing an interest in their music when you do see them would be a shared interest and a conversation topic.
As they grow up you might find they see things differently.
All best wishes.

I think that as long as you can afford it, keep giving and, as others have said, expect no thanks, other than from your son. I would strongly suspect that the children don't know about your contribution.
How are they when you see them? I can see that it is difficult when you see them so little, you wouldn't expect an easy conversation, but are they generally pleasant kids?
I see no harm at all in asking about the music and the school trips - it makes for conversation - and does indeed check that the money is being used as you intend

I'd also suggest that these are significant ages for ann interest in something like music - are you able to ask something along the lines of "Do you still like the music lessons - is it something you'll be keeping up now you're older?" or "Do you get music lessons at your secondary school - will you still want lessons outside of school?". That sort of feedback may give you a good deal of information.

If you are struggling financially, then you could maybe give some notice about stopping some of this support.

I do think it quite possible that you will get the thanks much later when the children grow up and realise what was going on. Tough for you

PS: should say that this seems a very different situation from the 'lack of manners' posts we sometimes get.

I don't see why you can't "hassle" your son, as you put it. He is their father after all and must share some responsibility. Assuming he has the GC sometimes, it wouldn't be too much to ask him to visit you with them or FaceTime and ask them to thank you. He could even encourage them to write thank you notes. Most kids won't do that sort of thing without parental guidance. Your son could suggest it very gently and without controversy surely. I feel your ire is directed at your ex DIL but your son has had 10 years to be proactive about this.

I don't think you can do anything after 10 years. What's your son been doing? Does he see his kids?
He should be the one thanking you and maintaining a relationship between you and his children, not your ex DIL especially after a decade and if you didn't have a good relationship with her.

Do the grandchildren know that their grandmother is paying for their music lessons and school trips abroad? Do they thank her personally for Christmas and birthday lessons?
If the answer is no, then time to tax her son with this, and arrange a visit when they are not interrupted by their mother's demands. Why only once a year?
If they are still separated the custody arrangements may not be clear; time for son to establish definite contact times. May be the daughter in law is being used as the scapegoat and he is happy to live in this inconclusive situation, with mother helping out.

Why should they thank u. Its a grand parents privilege to help

A grandparents privilege to help?
Can’t agree with that Mercedes, it’s common courtesy t o say thankyou for something given. It shows appreciation, and it’s just two words costing nothing.

Agree with you silverlining.
I can’t imagine why anyone would think it’s okay not to say thank you.

I think the issues around 'thanks' are these (OP may clarify)
I assume her son thanks her
The children probably don't know she pays
The ex- wife / DiL is upsetting her ex's family - how is OP supposed to tackle this? It seems that if she rocks the boat then her son and the GCs suffer.

Of course, she could, on her annual contact say to her GCs "you do know that I pay for........xxx?". How might a child react to that? You might hope they will say 'thank you' but I think they may well be rather thrown, and in a unfamiliar situation may react badly.

As for why it might be "OK not to say thank you" you would have to ask the bitter ex (and yes, we do only know one side).

'I know she couldn’t afford the extra lessons and trips without my contribution.'

Is your son paying anything towards his children?

What is your son doing to foster the relationship? It sounds as though none of you really speak to each other.

Why doesn't he bring them over to see you during his parenting time? Or arrange a weekly/monthly video call?

Do you speak to the kids yourself - on the phone or video calling? Even a text or e-mail? Have you asked them whether they are still enjoying the music lessons and want to continue with them?