I hope this comes off as respectful as it is intended, but as serious as it is intended to as well. You should not be shunning your daughter. You have no excuse to. You should NOT be joining your wife in this exercise. In fact if anything, you should be going out of your way to be with her and your grandchild with your wife knowing that this is important to you.
By doing this you are enabling the situation, and your relationship with your daughter cannot be authentic. Have you spoken to her about what you know?