How funny all these maybe your hard to get along with.
Cop out excuse. Your in laws sound horrid. Do what I now do, go away at Xmas or just don’t go. They don’t treat you like family so don’t go.

I know the feeling. No matter what you have to socialize. It's only for a few hours. Grandparents will always spoil kids. It's their job. Talk about with the spouse. Maybe some kind of agreement can come out of it. Talk to them about issues you have with them. Say to your children just because they say it's okay...it really isn't. Inlaws should respect you in your home no matter what. Toys come and go...children will loose interest soon enough. Wishing you luck.

Grandparents spoil kids .. get over it.
Unless your specifically set on buying your child that item then it should not even be a discussion.
I will take a stab in the dark and say you don’t sound that easy to get along with.

Make a food hamper

I love my in laws but we do the same thing every year which is stay at their house and have a bbq then call it a day while we miss out on my family’s Christmas Day where they make it all about the kids... we always ask our kids what they want to do and we pull through for them! Which is bbq at the beach and having games there... my poor kids get to miss out!

Defs go away for Christmas. Doesn't have to be far away to be fun.

Maybe you are the problem? Are you doing everything you can to make them feel comfortable?

Go away Christmas Eve. Stay the night away and spend xmas day away. You can’t avoid them forever but keeping the Day to yourself and your own little family will take some stress away. Make the night away part of your family’s Christmas present.

This doesn’t sound good. Why don’t you plan a beach holiday over the Xmas period? If you are away you’ll have to skip the family gathering. Good luck!