Beth and I took the children to see Legoland and California Adventure earlier this week. It seemed like a good time: Many schools (but not ours) have started, so the parks shouldn't be too crowded. Also, it was Beth's birthday.
Legoland was fun, having pretty much what you'd expect. There's something of a paradox, though: Fundamentally, the most fun Lego-related activity is to build stuff, but we can do that at home. If Legoland was closer, I'd probably get a membership and take the kids occasionally (they did have a good time!), but I don't think we'll be making the trip very often.
California Adventure was sort of strange: It's very much a Disney theme park, only without all the familiar attractions. They were fun, but I found myself wishing we could do some of the more familiar ones. Our family in particular kept running into the height requirements: The big roller-coaster had a 48" minimum, which disappointed Peter. He was (eventually) OK with riding the other coaster, though (There are only 2 in the park). Amber at 40", plus-or-minus, was disappointed several times. She enjoyed the flying ride enough to want to retry, only to be disappointed when they ruled her not-tall-enough the second time around. Similarly, there are some 42"-minimum areas in the wilderness-themed play area, which would have otherwise been ideal for Amber. (I'm mystified why the horizontal climbing wall has that high of a requirement.)
At the end, we watched the "World of Color" show, which was spectacular. It's by far the most impressive thing I've seen done with fountains, even without the other elements. It's strongly reminiscent of Fantasmic, but with more space, and a more suitable park layout. There wasn't particularly much story to it, but we were watching it for the effects anyway.
I'm not sure how often we'll go back: Park-hopper tickets are noticeably more expensive, and if I have to pick one park, it'll be Disneyland. If somehow we did a multi-day visit, park-hoppers would make sense, but the children don't really have the stamina for even a full single day. Amber fell asleep for the World of Color part, and Peter fell asleep while riding on my shoulders on the way back.
Overall, fun, and good to see with friends, but I don't think we'll do the trip the same way again.