It just really doesn't have to be that complicated. When questioned, I was told if I wanted presents I should believe - end of conversation. The trouble is all the overwrought explanations.
I guess it all depends on the kid, and the other sections of the child kid relationship. Some kids can handle finding out they were being lied to, some can't; some parents can manage to lie to their kids in a way that doesn't set the kid up for a major fall, some can't. If my mom ever tried to lay that kind of absolute on me there would have been open rebellion, I've never done well with ultimatums.
My sister tod me there had to be a Santa Claus "cause Daddy cant afford all this stuff"