If you ride every coaster, the freefall ride, and the flat rides at a nice casual pace, taking time to eat and go to the water attractions and water park, you can EASILY spend a good 10-12 hours in the park. With the Marine side now, I am sure everyone in the family will have something to do. 
 
10 Coasters + Freefall + Motion Sim 
8 or so flat rides 
3 Water Rides 
Water Park 
Marine Shows 
Boomtown Kiddie Area 
Sea World Kiddie Area 
A Few SF Shows (Batman, Magic, Country Music) 
 
That is all I can think of that is there, definately enough for a dya.