As an adult with a child, you are certainly welcome to make any plans that you want for the holiday season. If, however, your mom really gets into the holidays and wants all of her kids around her, it will be tricky to handle.
Mom, this year for Christmas and New Years' holiday, Tommy and I will be traveling to Paris. It's a wonderful opportunity for us to get away and reconnect with each other. It will be hard not being with you for those holidays, but it's the perfect time as he will be out of school during that time.
I'm thinking that before he and I take this trip, we could celebrate Christmas with you on December 22nd (or whatever day you pick). I'll cook the dinner and we can open our presents to each other after the meal, Will that work for you?
You need to make a plan to have some kind of celebration before you go - I think you will get less resistance that way. Don't let her spoil the holiday, but don't dismiss her feelings either. If you've always spent the holidays with her, this will be a big change for her. Good luck.