Well, for whatever its worth, here's another opinion.
SNA is easy. It is usually very expensive. You likely cannot get a direct flight into SNA.
LAX is slightly farther. It will be much cheaper. You can probably get a direct flight.
Best beaches: I grew up in Redondo (LA county), so I'm partial. If you want to stay in Orange County, Newport Beach is great. There is a decent boardwalk, decent parking, good beach/waves, Balboa is nearby. Laguna is fun because there are protected tidal pools. You can walk the area and see ocean life. There is also decent parking, and lots of good shops and restaurants.
Besides DL/CA, is there anything you've always wanted to do? If you want to see LA, consider changing hotels and staying in town. Here's a link re: LA hotels -
http://www.thegrovela.com/concierge/tourists/.
Do you want to go to San Diego? Again, consider changing hotels. Besides Sea World, Legoland, San Diego Zoo (awesome), and San Diego Wild Animal Park, there is Seaside Village (haven't been there in years), and the Gaslamp District.
I hope this is helpful. So Cal is really spread out. And its fun.