Husband and I have very different style as grandparents

If any of mine whined for a chocolate bar, there is no way they'd be given one either before OR after the meal.
To do so would reinforce their sense of entitlement. Whine and it shall be given. Never.
Some parents....

Stop placating these horrid grumpy old men..... they do it all for attention... "Concentrate on me,me,me, not on those kids" My husband is the same , my grandchildren refuse to even speak to their granddad unless prodded by me or their parents!! All because his nose has been 'put-out-of-joint' by their arrival and the time I like to spend with them.Can you believe a 72 year old being jealous of his own grandkids. It's not a pretty thought is it. Stop placating ladies.... It's them missing out!

Hi hear you JanaNana, but what about the fact that he shouts at the kids in a way that is actually scary? I am not talking about setting limits in our house, I completely agree with that and do too. It's his very aggressive manner towards them (not all the time, but quite often) that causes the problems between us, and between us and our DD

GabriellaG - that's exactly it. The pattern is that the kids want something, the parents say no, the kids whine and nag, and eventually the parents give in. So the kids learn to whine and nag and they will get what they want.
It drives me NUTS.
My DD and I have a very open relationship and we talk about it and she agrees with me but has this sort of "what can I do? approach - like she's helpless in face of the kids demands. She has a hectic life with 3 kids and 2 careers so I get it, but still.....

Children have to learn that everyone is different and they have to learn to get on with other people.

My DH has very little patience with children (he was the same with his own) and sees little of the GSs. The two youngest came round one day when he was out and the first comment was "Granddad's not here, we can shout!"

DH is generally very good with the DGC and plays a full on active grandad role with them..takes them out, plays games with them etc etc. but if there is an upset and I am already dealing with it he can't keep out of it and comes to add his 2penneth, even if he did not see what happened! It is really annoying!
He is also more particular than me re sticky fingers/ spillages etc and makes a huge fuss (imo) wiping tables, faces etc before they have finished eating, Drives me mad!
I do get them to wipe hands and faces (well the younger ones) before they get down..but only when they are done! However they all adore him ..so it can't be all bad!

PECS: wow, that's exactly what my DH does: if there is an upset and I am already dealing with it he can't keep out of it and comes to add his 2penneth, even if he did not see what happened! It is really annoying!
And of course DH adds his bit in a really angry voice so the whole thing escalates unnecessarily :-(

So lucky that OH is great with GCs- and that we have a lot of space for them to go a bit wild here. But he is much stricter than me ... same was with ours.

Many of my friends complain about the lack of patience from their GOM (Grumpy Old Man) with GCs, and being over strict - possibly as a reaction to the parents being just not strict enough.

Phillippa, I think the first thing here is to try to help dh remember to take his meds - for everyone's sake, not just the gc's. I think you've been given some great suggestions on how to do that.

Also, have you asked him to tone down the yelling? He may not realize how scary it is.

Can you minimize the occasions where these problems occur? For example, if the chocolate bar issue always comes up at lunch, then perhaps avoid having lunch together. Maybe see them after lunch or meet at the park, etc. Or provide other activities the kids can enjoy while the adults are having lunch, like coloring books or whatever, depending on their age. (I know they should eat lunch, but if their parents are going to give them chocolate bars, etc., then that's not going to happen.) Or if lunch is at your house, perhaps you can make sure there's no candy in the house? Then when the gc ask for a chocolate bar, you can just say, "Sorry, we don't have any."

I realize lunch was just an example. But, hopefully, there are ways to prevent other problems, as well. Neither you or dh are going to win the discipline battle with dd and sil. So, imo, you need to minimize the effect on you.

Imo, too, if dd's feeling helpless to deal with her own children, she and sil need some parenting classes or family counseling. But that, of course, is up to them.

Is it possible that dh would rather spend less time with the gc than you do? That might make things easier on everybody, too.

Starlady, great suggestions, thank you. Yes, DH would probably be happy to see them once a week and I am constantly telling him not to do more than he feels comfortable doing (he really doesn't have to). I just think that when he IS with them, he should try and make it more pleasant.... quality vs. quantity!
It's an ongoing struggle but the last few days have been better. I don't think it's a coincidence that this is since I've been on GN!
The support and reassurance here has been wonderful, I must say. Thank you all