I live in So Cal and don't do much stuff, but here is a listing of some things:
Knott's Berry Farm - the have Camp Snoopy for the youngins and big rides for the big kids
Seaworld - about 1½ hours south of
Disneyland
Legoland - about 1 hour or so south of Disneyland
Aquarium of the Pacific - north of Disneyland in Long Beach
The Queen Mary - north of Disneyland in Long Beach - although I haven't toured it, I don't know if the kids would enjoy this, but you might.
The California Science Center - in Los Angeles
The Discovery Science Center - in Santa Ana, a few miles south of Disneyland (a lot closer than TCSC)
Universal Studios - Hollywood - I haven't been in YEARS - I was pregnant with DD13 when I went, but not sure if there is anything fun for the kids
Santa Monica Pier
Balboa Fun Zone - Newport Beach
The Getty Museum - Los Angeles
LACMA - Los Angeles Museum of Art - Los Angeles
I googled "places to see in Los Angeles" and found some of these on the list as well. Hopefully you can find something to do when you are done with Disneyland.
Have fun!
Candace