I think the vast majority of the people are honest and just do the right thing. We went during the week of my daughter's third birthday a few years ago. She didn't use a pass on any day up to her birthday, and no one ever batted an eye. In fact, she didn't use a pass on the day of her actual birthday - I mean, hey, it was her birthday, and besides we got there early, and she wasn't born until later in the afternoon! But the next day she she used her park hopper, and did for the rest of the trip.