You're not that far from LA and could do the Hollywood attractions. Just remember that the traffic sucks around the LA/Orange County areas.

The drive down to San Diego isn't that long from Orange County either.

Newport Beach is a great place to be at night in Orange County.

With the sisters being that young, it seems you might be getting Disneyfied with Disneyland and the California Adventure. Knotts Berry Farm is up the road too.