M.D.
I heard a very funny story about a family who used the following method (although it will be hard on you for a while): He put them in their rooms and told them he "didn't want to see them, didn't want to hear them" until morning. When he saw or heard them, he gave them chores (sweeping the garage and the back porch, I think) until they were tired (and when they were cold he brought them a jacket ;-). Eventually they really wanted to go to bed and when he heard something he would just say "You must not be tired" and suddenly they were ;-)