I take it you'll have a car? You'll need one.
Santa Monica is pretty nice to hang out in, the pier is good fun and there's always stuff going on on the beach that you can watch for a few hours. The south beaches like Huntington are good for a sandy beach day if you want one - they have a relaxed surfer type feel to them. Hollywood is worth a visit, personally I wasn't keen but you can see the stars on the pavement etc and get as close to the sign as you can. I think you can get right next to it but we couldn't figure it out. We ended up on a hilly area and you could see it. You get an amazing view over LA from up there.
Disney is a great day out. It's obviously very commercial and cheesy, but they know how to do things right. Universal Studios was good when we first went, I assume it still is and it possibly better for older kids/young adults.
Beverley Hills house little house tour is OK if you like that sort of thing. I would just drive it and print your own map off. You can't see much, the houses pretty well hidden.
Other places - San Diego is only a couple of hours south. Politically incorrect to do Sea World but that's a great day out too. The zoo is supposed to be pretty awesome.
If you do decide to go to SF, take a day or two and go up route 1 - it's the coastal route between LA and SF. You'll probably only average 20 mph all the way but it's a lovely drive. It took us about 14 hours to go the other way, mainly stuck behind motor-homes and very slow moving traffic but the scenery is worth it. I'd do it again but stop overnight somewhere I think. Coming back, straight down the 5, wont't much more than 5 hours