OP, but things change. There's no way that decisions made when emotions are running high at the time of a split can be held forever.
My exh and I split up in the November. We spent that christmas together for many reasons. He'd already moved out. He bought and cooked all the food as he always had done.
The following christmas, he came to see the children open their presents and we all went out for dinner.
The following Christmas, he prepared some of the food for dinner and I prepared the rest and we ate at mine.
The following Christmas we decided it was no longer necessary to have Christmas dinner together as he was now living with a new partner. However, our daughter invited him without my knowledge. He arrived to my surprise but we made the most of it and spent a reasonable afternoon together.
We discussed it afterwards - he apologised for not checking with me before turning up - and decided that it was no longer necessary and came up with new Christmas arrangements.
I have no issue with his girlfriend. She treats my children well and they like her - what more could I want? Nowadays, they spend christmas in whichever household they choose - no pressure or expectations from either of us.
They take our children on holidays and I take them on holidays.
I've given up 'my' days with them when his girlfriend has asked if she can take them somewhere for the day - if that is what they want to do.
The point is that life and situations are constantly evolving. Wht was right then isnt necessarily what is right now and you need to let him live his own life and you live yours.
At the moment, you're just making a bit of a good of yourself, tbh