ETA
After reading all the posts I have to point out one thing. HE HAS AS MUCH RIGHT TO WANT TO SPEND THE HOLIDAYS WITH HIS FAMILY AS YOU HAVE THE RIGHT TO WANT TO SPEND THE HOLIDAYS WITH YOUR FAMILY.
Who decided the WIFE gets to decide this all on her own. Seriously? Moms, is it really like you're saying?
If HE wants to spend the holidays with his family he's not on his wife's side? He's a momma's boy? He is undermining his own family? Seriously?
If he has a good time with his family and is bored beyond words at your family activity maybe he is really trying to support you by going to your family first, making plans with YOUR FAMILY every single year first, and his family gets pushed to when YOU want to go over. You might even make alternate plans with your family but do you whine about it? Do you throw it in his face when you're talking about what to do on the holidays? Do you say I always leave my family to go to yours and I like my family better?
To me it seems like you and hubby need to sit down, like I said below, and YOU need to listen to him and accept maybe he likes his OWN family more than he likes yours. It's supposed to be that way, right? He was raised with these people and loves being with them as much as you love being with your family.
I think it should be 50/50 if you can't decide. You don't like her and she doesn't like you. Why not stay home or go to your parents by yourself and let him go where he wants to go. he'd probably enjoy the day more if he wasn't being pulled by you towards your family and then resenting having to leave your family to go to his.
This is why you guys have to have an honest and open conversation. He might hate going over to your parents house but does it to please you. He might hate going to his mom's house and having her act like that because she didn't get put first.
Both of you have to be completely honest and then go from there.
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I'd tell my husband to tell me what he wants to do. I'm sure he DOESN'T like being in the middle.
I would talk to your parents too. Are you the only ones that come to their house for the holidays? If so then see about inviting them out to eat with the whole group. That would set mother in law off wouldn't it?
I do have to say though, on holidays I don't know anyone who eats their big family meal at 6pm. Most are done with their big family meal by 4 or 5. Then if they get hungry before bedtime they go sneak more dessert or a turkey sandwich.
If this was me and I had to choose between my family and his I'd choose his because I like his family better. I enjoy my time there more and I laugh and hug and just overall love my time with them. If I felt that way about my family and not his but he felt that way about his family then I guess we'd split it and I'd go to mine and him to his. Kids with the one that has the most kids they enjoy being with.
Then after we ate and finished up and spent some time with my family we'd gather up and go to his family's house.
In all honesty I can't see eating 2 huge meals in one day like that though. My mom got us either the weekend before or the weekend after and his family got us on Thanksgiving. Mostly because it took us a couple of hours to get to my mom's house then driving back. Plus we had to work on the day before and I had my child care business back open for limited kids on Friday, Saturday, and Sunday. I had regulars that would have to take off work if I wasn't open so I opened for them on their regular hours.
Also, why not give out a calendar to both parents and start having some holidays at your house and invite both families? It doesn't have to be on the day either. It could be the weekend before or after. There are many things you can do. Some of them alienate mom's on both sides, some of them appease one but pushes the other aside, so you and your hubby have to sit down and decide what's what. You can disagree on this too.
All in all I'd make my decision on what "I'm" going to do after talking to hubby and the kids. If they all want to go to his family for the holiday and don't really want to go to your mom's then you might have to accept that and let your mom know you'll be going over there on the day of. I'd feel bad about that though. It's hard for sure.