Yeah, it's one of those..."Now you know the truth, we shall never speak of it again" type things, LOL.
I still sign the tags from Santa, Still put out the cookies, still put out the gifts in the middle of the night etc...
Sounds like we are confusin' the kid huh?? He's a smart kid. He knows we do all this cause it's part of the tradition and just downright fun. He also knows (and make sure your daughter does too) that many kids still believe, so she should not be the one to correct them. That's just mean.