I used to go to a catholic school and was probably the biggest christian out.
However upon doing something the church condemns (THINKING FOR ONESELF) i realised how much bullshit it is, and my family as followed suit.
However its what christmas is about rather than the tradition and event behind it that matters. I love seeing my family as you have mentioned, so i dont give a shit if i dont believe in it, (i actually hate religion) but i am not going to hate something that brings people together.
and also... PRESENTS!

in regards to your paragraph on Jesus' existence. I think thats crap IMO.
One of my favourite quotes ever is;
"What can be asserted without proof can be dismissed without proof."
The fact that the gospels were written 300 years after Jesus' existence and there is no real proof of him living somewhat erodes the credibility about the whole story of him living lmao