I don't know how old your kids are but Balboa is a good place to just explore; parks, museums, street performers etc. Old Town is fun and the Mormon Battalion is right around the corner. BTW, if you get a burrito at Cafe Coyote you can feed a family of 30. Obviously the temple, Padres game, or the Zoo. I have never been a fan of the Sea World, but you can take the kids to the UCSD oceanography museum. It's much cheaper than Sea World and, although it does not have rides, it's much more hands on.