I've got some real black, macabre humour for your situation, which I hope brings a smile.
A woman aged 102 years old decides to divorce her husband after a marriage of many decades. When asked why, after all that time, now she has decided to divorce? "I wanted to wait until all of the children were dead".
Your children are grown ups and whilst they might dislike it (yet again, you might find they don't mind at all and already see their father more clearly than you have), they can cope with this.
What would really ruin Christmas would be the tension of two people who are in conflict and preparing to divorce one another, trying to pretend otherwise. Or, if the pretence were successful, your adult children looking back and feeling deceived by you both.
You have been hurt. You deserve consideration and care in this situation. And not to give one minute more of your life than necessary, to this selfish deceitful man.
Find some people who will provide the support you need and deserve, and surround yourself with them at Christmas. Hopefully, that might be your adult children, but if they can't handle it because of the relationship they have with their dad, then I'd suggest you give both them and yourself some grace by changing your plans.