We had tickets for Universal. It was a 5 day pass but you were able to use them spread out over the course of a year (purchased at costco).
We went once by ourselves. We planned on going back and taking our daughter, but it just wasn't worth it. We did everything in a day, and most of the stuff was not for young kids. Don't get me wrong there were tons of little ones, but they usually ended up crying on the virtual rides they were allowed on and the parents took them on. The studio tour, while interesting to me, was long (a long wait too), a tad on the boring side, and the King Kong 3D experience jerks the tour car around...yeah lots of little screaming kids. A lot of the virtual rides have age requirements (the Simpsons was one of them). House of Horror would be too scary for kids. Terminator has lots of smoke and loud gun shots going off. I think you get the idea.
Really the only attractions for small children are the water play area and the Shrek adevnture. If they could sit still for the Hollywood animal show they might enjoy that too.
We had fun as an adult couple, but like I said...wasn't worth going back with our daughter. I would skip it with the little ones. Legoland is awesome and so is the Zoo!
Good Luck =)