L.F.
It has always been my rule that if they ask I deny but if they tell I confirm. 2 years ago my now 12 y.o. son told me that he knew I was the tooth fairy. I confirmed. It was only a short leap for him to know that Dad and I were Santa & the Easter Bunny.
My now 10 y.o. old dtr does not let on either way so we still go on the assumption that everyone still exists for her. She was asking regularly when she was in 1st grade b/c another kid in her class ( a non-believer with a different religious upbringing) was taking it upon herself to tell everyone the truth. I wasn't ready to let it go just yet so I asked her what she thought and she quickly replied that there is no way her Dad and I would ever buy all those presents for her and her brother - it had to be Santa. An so....the dream lived on.