Wow, Athea!
I'm in disbelief! I am so sorry you were treated so poorly. I do not know their side of the story, but no matter what their side is, the way you were treated is unacceptable.
I think it's time you sit down and have a talk with your husband. For your husband to have allowed this, and even participated in it, is appalling and he needs to know how you feel and this kind of behavior from he or your in-laws will not be tolerated, EVER!. Your in-laws, and your husband, have deceived you and have negated your rights as a wife and mother to their neices/nephews/grandchildren.
You might take the advice of the post who offered her business card for counseling services. I have a feeling, from your description of your husband, that he would never participate in a counseling attempt. But it's my advice that you should go and try to figure out how you will deal with this very controlling extended family of yours.
I'm trying to figure out why you wouldn't have stopped at the altar after you were excluded from planning your own wedding. In stark contrast to another ost that implied you are controlling, I think you are too passive. You cannot continue to let this family walk all over you. You are going to have to stand up for yourself and hold your ground. I am sorry for you and for your children to have to watch there mother being beat down by their father and his family.
Godspeed to you, Athea.