As long as you never say it is actually real, There's no harm done but you technically can't disprove a negative. My mom helped me write letters to Santa but never actually said he's real and dad never impersonated him or left cookies out for him- that was our initiative. We also tried to set up trip wires attached to bells and walkie-talkies to try to catch him. They let me and my siblings have fun with it the same way they let us tie blankies around our necks and be super heroes. If only they where as wise concerning religion.