I believe my son knows in his heart that the relationship that he has with us is not a choice that he would make for him (or his kids). I believe it makes his life easier to go along with wife's wishes not to spend time with us. So it works for him. Sad, but his choice.
If the get togethers are hurtful, I stay away and ask to visit on a different day when her mom is not there. I seem to allow them to make me feel invisible and unworthy if I attend when all eyes are on the "wonderful, perfect" grandma.
Keep coming here when you are down. It will get better. Remember that you did your best to be a great Mom, and hopefully, in his heart, your son knows that.