It depends on when you start telling them, really.
Well, if your are telling you kids about Santa for 10 years, buy them a helmet, cause they're going to be bouncing around in the back of the bus. And (I almost have to laugh at this run of stupidity), if your kids develop actual mistrust because you told them about Santa, holy shit, no amount of therapy will ever mend that. So, I guess I get your irrational point of view. And personally, I think it's horseshit. But do what you want. I just appreciate the chuckles from this thread.