Mil is 60 this year. And she and fil are celebrating their ruby wedding anniversary. They were talking about how to celebrate it. They don't want a party or anything like that. We suggested they come on holiday with us for a week in France in August as a celebration. They agreed. We're going for two, they'll join us for the second week.
Now I think they're ok as people. They're very needy, try and centre their lives around their grown up children and the gcs. Mil has never worked outside of the home, has had three or four nervous breakdowns because she says she doesn't see the gcs enough, can be very interfering, tells stupid fibs about ridiculous things, has bonkers logic and is big on emotional blackmail. Other than that, she's fine 
. Fil is a spoilt prince who dislikes anyone disagreeing with him but he's quite bright and can be entertaining.
So, this week away with them could be quite trying for me but seeing as it's such a big year for them, then why not? They never went away with their parents and the gcs. In fact, mil struggled to have her mil over for supper once in a while.
Anyway, it turns out they've organised an event - visiting some chocolate world thing - with dh's sister and they want us to go to that as well to celebrate their wedding anniversary. We said no because we were going to France with them, we will have just seen them two weeks before, dh doesn't particularly want to see his sister and we've already agreed to attend two children's parties that weekend. Now, if it were me, I'd've just said we were busy but dh really spelled it out to them which I think was unnecessary.
Fil went bonkers on the 'phone, saying this wedding anniversary was a one off, didn't dh care enough about them, he never sees his sister (dh replied his sister is a racist c* 
who never bothers to visit when she's down south anyway) and repeated that we were taking them to France this summer to celebrate and that was enough - they're not paying either, our treat. He then put the 'phone down on his dad, telling him he was a stupid old man. Yikes.
Next fil leaves two messages on dh's phone begging him not to turn his back on him, he loves him etc etc. Really heavy stuff. Dh wanted me to listen to them as he couldn't bear it, he was so angry with his dad for laying on the guilts about some stupid trip.
Then fil calls me on my phone and recounts the conversation back but only dh's words, not his. Basically looking for my support. I don't give it and reiterate what our position is but I feel really p*ssed off that he has tried to involve me against dh and that our taking them on holiday this summer just isn't enough for them. Grrrr. Dh wants to cancel the holiday, well, their part of it but I can't do that because it would make for really bad feeling but they are behaving like spoilt children.
Do I just back off and just refuse to get involved and quietly support dh in whatever he decides?