We lived in the area for many years.
Besides Sea World and the other attractions mentioned The Wild Animal park is amazing! It is located inland and was dedicated by the San Diego Zoo for breeding endangered species.
In the seventies it was initially designed as a facility closed to the public. But the educational opportunity and income potential was just too great to pass up. You'll need a car or will have to find transportation, but it will be worth the hassle. First get an overview by riding a monorail around an enormous enclosure where free ranging animals are separated only by continent of origin. Of course predators and cantankerous/agressive animals are kept in their own enclosures.
There are plenty of walking trails and entertainment arenas.
http://sandiegozoo.reachlocal.com/co..._id=9893922799
There is also the Embarcadero area downtown with the Martitime Museum, Harbor tour boats, the retired aircraft carrier the USS Midway and lots of shopping in nearby Seaport Village.
http://www.family-vacation-getaways-...barcadero.html