If you have breakfast provided in the hotel, eat a big breakfast, and then just take snacks to the park, saves buying food in the parks as this can be expensive and adds up quickly. Take a small cooler bag with you and some ziplock bags, you can make a freezer pack by filling up the ziplock with ice from the machines in the hotel. Keeps drinks/snacks nice and cool if the weather is very hot.
Definately check out some of the restaurant websites before you go, and sign up for any offers/deals they may have. Can be a very cheap way of eating, we went to Sweet Tomatoes at least 4 times in a fortnight, getting vouchers before we went, and it cost us $24.99 for four including drinks for an all you can eat buffet.
Have a couple of nights getting a takeaway pizza, these tend to be huge and cheap, and are good for filling up hungry teenagers!
The hotels will also have voucher books for various restaurants in the lobby. Or ask the concierge who may know which local restaurants have deals on.There are usually vouchers for offers on entertainment as well, such as crazy golf, wonderworks etc if you are into those sort of things.