Ah, it's just a game, adults get fer too hung up about FC IMO! Stop being so adulty and try a bit harder to think like a child!
"should we forget about xmas then?"
This is exactly what I mean! Stop beign so literal!
Did you ever tell your child they're not allowed to play a pretend game because really they know it's not real? No? Well why does FC have to stop if they know really it's not true? Santa a lovely game that even all the grown ups get involved with.
I don't remember ever believing in Father Christmas. One of my early memories is overhearing other DC in reception talking about Santa and knowing he wasn't real!
But - sometimes I did think he was real again. My parents never admitted it either way. I remember one Christmas Eve trying really hard to stay up late enough to prove to myself it was my parents! Although I knew it wasn't real I still had a what if and played along.
And even when I knew for sure, I still really enjoyed it and it still felt magical. Christmas is magical when you're a child, whether FC is real or not!
I suspect my DS knows Santa isn't real. When he asks, I say "what do you think?" and "that's an interesting idea". I don't lie to him, I smile and be mysterious and turn it into a joke / game and he doesn't push it. If it seemed really important to him to hear it from me, I'd fess up, but we're not there yet.
I'd do your DS a stocking, and if he says it's from you, smille and say "what an interesting theory" and walk away!
Please don't feel awkward. Remember it's meant to be a fun game, you've just moved up a level! The loss of innocence stuff is nonsense, honestly. He's still a child with a sense of wonder about the world.
Great he's got religion sussed btw, I'd be proud of him for that!