CHRISTIAN PARENTS of ESTRANGED ADULT CHILDREN Community Group
Estrangement makes it difficult to talk about with family, friends, neighbors and church members. Christians are NOT immune to broken families. Talk about your experiences with those who know how you feel and get positive support through your Christian faith...."In these last days difficult times will come, for men will be lovers of self...disobedient to parents,...

I think some counseling is in order too.
You are correct in one thing though...going to sons wedding is a one time event...and one most of us would not want to miss...but he will be going on with his new life after the wedding (new wife...kids...family etc) which is as it should be of course. He will not be stepping in to take over his fathers place (your husband) in your life as far as support etc.
My suggestion is to go to the wedding with DH as it should be and let your son see you are united and he can take the next step.
Blessings...its a tough one !
AllK