Glam, Can you get a email address for your son's father? That might be better than ringing him up. If you do speak to him, the words will come at the proper time. Do not be afraid of him for he can no longer hurt you or your son.
As for your h, don't offer up an invitation to come over. That may be putting him on the spot. If you call, wish him a very Merry Christmas and let it go. He needs to come to you this time and not the other way around.
Christmas is the time for giving and showing compassion to those who are less fortunate than we are. I suspect both h's are feeling some remorse for what they've done to you and their family. Take the high road Glam and show them that you can be that classy lady in any situation.
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.