K.Y.
Definitly stay near Sea World if you can so that you can leave and come back if the kids (or you :) ) need a break. When we went we spend two days at the park, one for the shows, etc. and one for the water park. The water park day we rented a private cabana which was well worth the money. They take your lunch order, have drinks on hand and you have a good home base to keep everthing you need when you have small kids. I was able to pull the curtain on the cabana and get my littlest one to take a quick nap while my husband entertained my oldest. We also did the dinner with Shamu thing - my son was a little over 4 when we went and he loved it, of course it didn't mean that much to the baby but it was still pretty fun. Have a great trip!