Everybody loves something free. Create a customer loyalty program to encourage you customers to come back and earn points towards some goal such as free concession, admission, whatever you decide. You control what earns reward points, what the rewards are, and the expiration of the reward offers.
Pre-Paid gift cards are an opportunity to increase sales that most rinks miss out on. Gift cards basically fall into one of two categories. Used and unused. Both are profitable. Unused gift cards are pure profit. Used gift cards often exceed the orginal amount of the gift card with the customer paying for the additional amount.