My advice is: Don’t let your beliefs separate you from friends and family.
Participate.
Christmas is far more a pagan/atheists holy day than it is Christian. Christianity was, from the beginning, mixed with paganism for the purpose of unifying the Roman empire. If Jesus had his way Christians would go to church on the sabbath (Saturday) as was his custom. But they go on Sunday (most) because their religion was constructed to bridge the gaps between religions and secular society. And clearly, the Empire didn’t think it was a big deal to merge all of this stuff because they didn’t take religion as seriously as many take it today. That too is something we need to learn from.
If you take it too seriously, you will isolate yourself from believers in a way that doesn’t help anyone or anything. If they want to pray over their food, fine. Treat like a kid with an imaginary friend. Do you absolutely have to shut it down? Are you going to shut down the imaginary friendships of millions of children? Are you going to crusade against them or refuse to parent children who have imaginary friends? Of course not. So treat it like that. When believers see you participating to the level that you can, then you will seem less alien to them. You will seem less of an extremist to them. They process your lack of participation as you being extreme, not as you standing your ground against their beliefs. So no matter how you think about what you’re doing, try to consider it from their perspective. And don’t be a Grinch. Buy gifts. Do whatever.
Most of that stuff has nothing to do with Jesus anyway.