Every year on here there are these threads, and I find them depressing 
Not you, OP, but there are usually a few threads about "lying" to your children, and the ins and outs of the Santa story
As far as I am concerned, Christmas lost a great deal of its sparkle when I knew. A friend tried to tell me at 7, but I refused to listen, and continued to "believe" even when I probably knew deep down it wasn't true, just because I wanted to believe.
My feeling is that there is such a short period in your life when magic is real, when the world is exciting and mystical, when good things happen to good people. Then you grow up.
dd1 (7) I suspect has her doubts. she has asked me lots of questions about how Santa gets round the world- I bamboozled her with Einstein's theory of relativity and I think we got away with it for a while (science of Santa
) But she wants to believe, I can see that. So I facilitate it, because it makes the whole thing so much more exciting and wondrous. We are a family big on magic and fairy tales (I myself am a trained troll-killer, as was my father before me)
I think you can still pull it back, OP. I can understand why you are upset. Childhood is such a short magical time , and I'm all for making it as long as possible