I was in this position last year. I decided to not do anything as a family. It was upsetting at the time, but if things don't work out, chances are this is how it will pan out in the future anyway ( ie future christmas days etc )..
I'm 12 months ahead of you and the best advice i can give is live for the kids and live for yourself..
I am in a better position that i was 12 months ago, and i know i'm the better parent. The children see this and its me they want to be with ( although she has them 60 / 40 ) - but they are with me on Chistmas day and most of the holidays - why ? ? ? - Becuase they enjoy being at my house more ( their words ) and they know when with me, they will have my full attention and fun.. I dont sit their with my head wrapped in my phone like WW does..
Make XMas about the kids and you - not her.
Previous username - Helpme123.. A name chosen at a desperate time..
Now Mr Brightside.. coming out of my cage, and doing just fine.