If you rent a car, find a way to get to the Buena vista outlet mall. Seaworld is maybe 5-7 min east along I-4 from there. Behind the Buena vista outlets and surrounding it, are several restaurants ( including outback/carrabbas/lone star, etc) and a publix hidden away behind the mall. Down 192 in either direction are target/ walmart ( also a wal mart on sand lake road close to Seaworld) both of which have groceries and for the health conscious, there is a whole foods and cafe there as well, Also higher end restaurants all along the Dr Phillips area maybe 10 min away and on I Drive.
Enjoy your trip and dont be afraid to explore a little! there is a lot more to do down there other than disney, but you can easily spend your entire time there and not have to leave DIS property at all too.