I take a small purse-type cooler. In it: 2-20 oz frozen bottles of water, some granola bars and gum. By the end of the day, I have replaced the water bottles with souveneirs.
Once the drinks are out, I have found the insulated cooler is also a great place to put my camera on the wet rides.
I certainly do not have a problem purchasing drinks and snacks in the park and often have to get more water. But, I typically don't think about being hungry or thirsty until I am standing in line for a ride.