Was raised modern orthodox Jew here, so can't really comment specifically on my own experiences...

But I can say some things on general principles: Treat kids fairly.

If you (as a parent) are going to be the sort of parent that punishes your kids for lying to you, then you'd better not be systematically lying to them (I'm not talking about lies-to-children, which can easily be presented in an non-deceptive way. Santa is NOT, however, that sort of thing at all. Santa is a blatant deception.)