C.H.
After four years of being treated this way, I wouldn't even consider making the trip. That's just masochism. Plus, you're teaching your children to jump through hoops for people who don't respect you. You should chat with a psychologist who probably has a very easy response to this behavioral pattern, just to put it in perspective for you. Otherwise, you'll still have this same problem in 5 years, ten years, 15 years, you know?
By the way, my brother's married to an awful woman (he knows that), so I've never travelled 2000 miles to visit them). Why on earth would I use up my vacation time and family money on a woman who is awful? (She's a spousal abuser and screams at her kids too.) I would just spend the whole time cringing at the family dynamics. My other siblings and husbands are in complete agreement that it would be foolish to drive that far to be in that household.
Good luck to you, and please treat yourself kindly.