Thanks for coming back in and responding to our posts, Panda. You sound like a very loving, reasonable wife, mum and GM.
I'm sorry your GC are so unruly, and I'm surprised ODD and SIL aren't more concerned about that. If you don't feel comfortable bringing them to your home, then I suppose you'll have to take them out but, again, perhaps cut back on how often. If they are too hard to handle, you might have to let ODD know you can't deal w/ them anymore. But then, you may not get much chance to see them, I'm afraid. Only you can know what will work best for you.
I'm a little confused on one point, however. In your OP you said, "After trying to reason with her as she and her husband to be banned my other daughter from the wedding..."
But now you tell us, "I would like to say I absolutely didn't pick sides, I did say that I understood her reasons and it was her big day. "
I'm not sure how those two statements go together. In the first one, it sounds as if you tried to convince ODD to include YDD after all. In the second, it sounds as if you respected ODD's decision. Perhaps you did both? Gave her reasons why she should include YDD but listened to and accepted her (ODD's) reasons why she wouldn't? I totally understand that. But if ODD has always been "her way or no way," chances are she didn't. Chances are, she felt that while you accepted her decision in the end, you were really fighting for YDD. I'm so sorry about this. But I'm sure that - and the fact that you showed up at her wedding even though she basically asked you not to (sigh) - are at the bottom of this rift.
Also, maybe you and DH have done "far too much" and now, ODD just expects it? No doubt, you did it all out of love, though, for her and your GC. Perhaps it's time to stop doing so much. I don't think totally pulling the rug out from under her (refusing to babysit, period) would be productive. But, once again, I definitely would consider cutting back. What do you think?