You don't sign a contract to buy a shirt., but if you really want to go down the shirt analogy path. If someone shows they are willing to buy a $1,000 shirt from you, you don't let them go buy a $75 shirt from your competitor. You give them a $75 shirt to keep them from walking into the competitors store.
But if you are a theme park, and have 10,000 customers in your hotels, you do whatever it takes to keep those people on property, in the parks, and at citwalk. Hell a park buyout is probably part of the contract. Give them the tickets. You'll make it up on them staying on property eating and buying merch. The only way I see a pop warner organized group going to Disney is if they either stipulated it in their contract or if they also do at least one night at the Uni parks.