I tell my passengers that it would be about as risky as motorcycling, except that I cheat by making sure I've got enough fuel, only taking off in weather I can cope with, choosing not to play silly buggers with aerobatics at low level, etc.
I make sure as part of the expectation management that they are expecting a weather cancellation as likely as not. I have, as a result, never ever had any pressure from prospective passengers to take off when I wasn't completely happy.