Plan to spend a day at Catalina, if you go.
At least to go to Universal, even if you don't visit the theme park, there's a little themed shopping center right outside.
Go visit Hollywood while you're there, the walk of fame, hang around Hollywood and Highland you'll be fine. If you want a chance at the stars, get yourself to Rodeo drive.
Definitely go to Santa Monica, it's close to Maliboo (north) and a few miles away from Venice (south) so you can actually hit up three beaches at almost the same time. Each has its own flavor.
Depends on what you want to do or your taste, wine tasting is great. From where you are, Temecula would be a better choice for that. There are plenty of day passes to be found on the net. Visit Irvine Spectrum, South Coast Plaza, Fashion Island in Newport Beach, if you want shopping. Now, this is not what I would normally recommend to tourists, but if you like a laid back small city feel that's near LA with a buncha great restaurants and a nice shopping experience, come to Old Town Pasadena.
There are a lot more to do, but that'll do for now.