My parents did the Santa thing, and at least when I and my brothers were young they played it seriously (e.g. gifts from Santa had a different wrapping paper and different handwriting on the tags than gifts from Mom and Dad). I never came right out and asked them whether Santa was real or not. But I do remember one year (I’m not sure what age) thinking that probably Santa Claus was just Mom and Dad, but not knowing for certain, and worrying that I’d have to get the issue settled for sure one way or the other before I had kids of my own. (So that means I didn’t have a moment of revelation or disillusionment; the realization came upon me gradually.)
Anyway, I’m glad my parents did Santa, and I think it enriched me, for reasons I’ve mentioned in earlier threads: