I have been 5 times, I believe.
I havent found any must eats at SeaWorld. I havent been a fan of the food there
Must dos:
Depending on which animal(s) your family is interested in, the tours are neat. We did the shark encounter at seaworld. We touched a tiny shark and got to see behind the scenes of the underwater tunnel.
We have wanted to do the penguin encounter but it is booked quickly.
I cant speak for all encounters though.
the seal lion show is pretty good. It usually has the most issues as far as animal cooperation so it can get pretty funny. The shows in general are usually good and worth seeing. You will need to get to the Orca show early as that show fills up quickly. plan your day around the shows and when to be in certain portions of the park.
My wife loves penguins so going to the penguin exhibit is always a must for us. Its really, really cold in there. So if you love penguins, bring a long sleeve tshirt in your bag to give yourself a couple minutes more of tolerance.
While im not huge fan of paying to feed animals, having a sting ray come by and suck food from between your fingers is a different experience. Seeing the sea lions is cool but watching other people feed them is fine. They get really noisy (in case you have a noise sensitive person).
as far as rides, any of the coasters are easy choices. My wife and oldest son love Mako, especially.