I agree w/the others...wait until you are much closer to the time. I would have your h tell them while you are sitting in the room. It's his story to tell and you shouldn't have to be the one to break the news to them. You will need to be the one who will reassure and love them after he breaks the news.
Now, if he starts telling tales or speaking in a negative way about your or the marriage, then step in.
It won't be easy, but you will be there to reassure your children. He's not capable of doing that.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
