If your wife doesn't want to go to your Mom's, I wouldn't push it. I had a similar sitch here w/my family yesterday -- my H kept changing his mind about coming. I told him: "We're eating at 5. We'd love to have you come, but if it's going to work, then fine." He didn't come.
You don't want to force, guilt, shame them etc., into attending these events. In that case, it might go badly -- and if your W doesn't go, you can concentrate on having a good time with the people who are there with you.
The nice thing for me was - no H means no possiblity of drama. In a way it was a relief not to have him there - than I was able to relax and have fun.
