I'm so lucky I don't have this problem.
My boyfriend and I have a long-distance relationship, so we spend Christmas day with our own families and then spend Boxing Day until New Year together.
My mum and dad are divorced, but (and I'm aware this seems strange!) we have all spent it together for the last few years; mum, dad, their partners, us kids, grandparents, etc. Obviously my parents wouldn't spend it together if it wasn't for us and my niece, but it's lovely.
We're spending it separately this year, so my mum gets a break from being the hostess, so we'll spend the morning and lunch with her and then in the evening, we'll all traipse over to my dad's for the night.
Christmas is about your kids and you should spend the day however you like for them. I hope you manage to sort it out, I can see myself having a similar problem if my boyfriend has moved down here by next Christmas! :o|