I just got back from a trip to So. Cal which included Universal. I've been there several times before, and one day is fine. As long as you get there early, one day is fine, 2 days is waaaay too much.
Van Helsing is now just a Universal monster / horror house, it's like a haunted house walk through. If you're traveling with wheelchair or scooter bound members the walkthrough is probably not a good idea, it's possible but may be dangerous since it's dark, and there's unpredictable teenagers inside which scare easily.
They're pretty strict about bringing in outside food and drinks, so hide well.
Disneyland is very laid back with this policy, we have not had any problems.
Depending on health and age of you members, must sees include:
Water World show
Terminator 4-D show
Shrek 4-D
Tram Tour
The Mummy
Jurassic Park
I like the special FX show
The Simpsons ride is so-so, but it's new so check it out.