Celebrating xmas

I want to ask what you guys think about this. I had a little bit of a fight (argument). With foster family. They litterly raised, since my biological parents did not. They are christian, while my real parents. Who I also see, and myself, I later on became Muslim. Since then, I really just hate this month of december. Every year I get a invite for dinner with second Xmasday. (Here it's two days). And they want the whole family to attend. But I'm Muslim, while they are atheist except for one of there daughters is christian. They say it is about food only and not religious. Can I just go there and eat with them for the sake of having a good bond, not offending them? They litterly felt hurt, cause I invited them with Eid lfitr, which we celebrated, took them to the mosque and they even have a Quran.

So what to do now, in this context, I honestly would just like to eat them, (it's halal food) for the sake of our bond.