Your question was: Christmas planning.
I don't think it's fair to ask him to not see his father for Christmas just because you want to be with him. Afterall, you don't want to go with him and give up seeing your family just to be with him. And just because he hasn't spent some Christmases with his father doesn't mean that it's okay to ask him to give up seeing him this year..
I think you should just accept that you will spending the Christmas holidays apart. Make fun plans for New Year's, and you can look forward to reuniting!..
Yours is a difficult situation that many families have to deal with on a yearly basis and there is no way to please everyone 100%. Why not spend Thanksgiving with one family and Christmas with the other?..
I know it's difficult to please every family on the holidays especially one where the parents are divorced. How about spending Christmas eve with his mom, then on Christmas day you go to your family's and he goes to his dads? I know you sound like you really want him to be with your family but I can't think of anything else that sounds like a better compromise.There have been years that I've had to squeeze 2 families in one day...
Well you don't have to make rock solid plans yet - Xmas is still months away. And he is happy at the thought of sharing his holiday with you so that's a great starting point. So continue discussing it casually and trying to reach a happy compromise. I assume you'll be together New Year's Eve.
Perhaps there can be 2 Christmases - the two of you spend one with your family, one with his....