Definitely set aside time for Shamu's Happy Harbor. Your three year olds, in particular, will love the kid-centered area.
They would also probably really enjoy feeding some of the animals. That might be worth budgeting for.
Shamu is often near the front gate, so if they like characters, they should be able to meet him at some point during the day.
Don't skip the shows....even the little ones can be quite enamored with the dolphins, whales, sea lions, and the animals in Pets Ahoy.