For fun, for those ages, I would rank Clyde and Seamore as the funniest show, with Shamu having the most "wow" factor, Pets ahoy is the "cutsiest " show ( a bit too cutesy possibly for teenagers) . For learning about conservation the Manatees is a must do. Kids that age love to feed the dolphins, seals/sealions and the stingrays. There are good walkthrough exibits for sharks and penguins. Wild Arctic has a simulator ride at the begining of a walkthrough that generally is popular with youngsters as well. Nearly forgot, Cirque de la Mer is a pretty good show as well. If you've ever thought about going to Cirque du Soleil but balked at the $$$$ cost, here's a free show that has a couple of acts that are similar in style to the more expensive du Soleil.
It's easy to need more than just one day for SW, particularly with younger kids who like to spend time at the feeding exibits and in Shamu's happy harbour playground. If it fits into your schedule second "free day" at SW is usually one that's wel spent. ( SW usually offers 2nd day free if used within 7 days of your first visit. The booths to validate your ticket for this are just inside the park, on your left as you enter.