Hi Nicole,
If I'm understanding correctly, you are going to want a total of 3 days at Walt Disney World ( 2 at the Magic Kingdom and 1 at the Animal Kingdom). In addition, you want to visit a different theme park off property. You'll need to contact Sea World about what transportation options they offer, but I know there are several companies that have a shuttle from Disney to there and back.
Staying in a Disney Resort can save you a lot of money on a rental car, as transportation is free from the airport as well as once you get on property. If you are looking for great affordable options, you'll want to focus on the
Value Resorts. You can then purchase a 3 day Magic Your Way Base ticket. You won't need the Park Hopper, since you know which parks you want to visit and you don't plan on going to the others. This will save you some money as well.
Hope you have a wonderful vacation,
Kaylene