I can identify with your W's strong feelings toward your family. I went through similar issues. I never asked my H to cut them out of his life, but there was a point that I told him I was not going over to their house as much and from then on.....my R with his mother would change.
He had slowly (ever so slowly) begin to get his eyes open just a crack, and he did not put pressure on me like he had in the past. This was a great relief factor to me, and it put me in a much better mood. Many times I would angry at his mother and it transferred over to him. So, it really helped our MR in that particular area.
My suggestion is to tell her you will not pressure her to ever go where they plan to attend, but that if she ever decides to try, she'll have your support all the way. (This is so important for her to KNOW you will back her up, and if necessary stand with her over your parents. Not something you hope to do, but just her knowing you would, if push came to solve, will give her a sense of relief.)
You know this is dead serious with her, or at least you should know it is. You will do your M a favor by giving her this gift. For me, it was like setting me free of a terrible bondage. I believe it will relieve pressure on the MR. Won't settle all problems, but this is one that is really crowding her emotions, as the holidays are getting closer.
If she doesn't want to go where they will be, let her do whatever she wants to plan for herself. You don't have to figure some way out for her. Tell your family she did not feel comfortable about it. Surely they won't ask anymore, if they are smart.
FWIW, I never completely stopped going to see my MIL. I did attend family events. Things did get better, but I never allowed her to get in my MR again. Honestly, there was a lot of damage, and after all these years it still saddens me that my H would not man up sooner. I believe our R would have been different/better without her influence, but I don't obsess over it now. When she was dying, I helped sit with her. Not out of any particular reason other than she was my H's mother and it was out of my love for him that I did it. However, there was a time that I'm not so sure I would have been able to do it. I think that is the place your W is in at this time.
Maybe in time, things will get better between her and your family, but it may take years. No pressure, no expectations, okay?
It is not about what you feel should work in your M. It is about doing the work that gets the right results. Do what works!
