Santa Monica is fun, too (it's right next to Venice Beach). I go there a couple of times a year. There's the beach, the pier (which has amusement park rides, restaurants, a small aquarium, street performers, street artists--I have a small painting I bought that I watched being painted; it's actually a finger painting, though I wouldn't believe it if I hadn't seen it myself). There's also the 3rd Street Promenade, which is a giant indoor/outdoor mall with street performers, restaurants, shopping (much of it reasonably affordable), and even a 3-story Barnes and Noble drool .

Also, agreeing about Carlsbad--that's the beach I most often went to as a kid. Oceanside is nice, too. Newport Beach is great for walking, but trying to find a parking space is like finding a needle in a haystack. Knott's Berry Farm is great for teens--the high school I work for has an annual trip there for the students who raised their scores on the standardized tests (or stayed at the top). The kids love going on this trip.

"Oh, you can’t help that," said the Cat: "we’re all mad here. I’m mad. You’re mad."
"How do you know I’m mad?" said Alice.
"You must be," said the Cat, "or you wouldn’t have come here.”

- Lewis Carroll, Alice in Wonderland