Can I run a raffle if I don't get anything?

If I work at a student-housing property, and the business wants to do a give-away at a field-day event, can we run a raffle in which we give away a prize? The raffle would not be paid for by the entrants, but instead each ticket would be earned by participating in our event. If someone entered a potato-sack race, for instance, we would give them a ticket for participating. They could then use those tickets for a chance to win a prize such as a bicycle, an i-pad, etc. We would provide the prize for them, and would not profit from this event. As we like to hold event, we thought doing a giveaway would be fun for the residents, however, we wanted it to be fair as well as promote participation. Is this something that we can do, or would we need to go with a different route?