We love California disney etc!
Universal was great when we went. That was before the fire there so I don't know what it's like now.
The excitment starts as soon as you go in with the travelator type things to get you up and down the slopes. Don't get distracted by the nickelodeon water park, come back to that later when the kids can get soaked. Take some flip flops with you so they don't get their shoes soak, they're very insistant in usa that shoes be worn in splash parks.
Do the big rides like jurassic park and mummy's revenge as early as you can and then do a backlot tour later when it's hotter and you want a sit down. The backlot sounded like it would be boring, but you get caught in a flash flood and there are dancing cars flying at you with flames and stuff along with the tour through the sets etc. Really excellent.
Knotts Berry Farm great for roller coaster junkies (my ds is one), but completely lacking in theme and doesn't have any of the detail of disney. My ds was oblivious to any of that though and loved it. I did send him off on most of the roller coasters on his own though, there's a lot of loops!
Disney - We love both parks (disneyland and California adventure). Definitely get there as early as possible, get on the big rides and get fast passes. Then go back to hotel for rest and go back in evening. Would suggest you stick to one park though, as you end up hopping back and forth for to avoid queues when in fact if one place is busy the other is too. The only exception would be to move from california adventure to disney in teh evening when california adventure shuts earlier sometimes.
Definitely use the fast pass system. And don't aim to do it all in one day either. We spent 5 days at the parks and we didn't get everything done each day but didn't worry too much if a queue was too long as we just made it first call the next time). Defintely plan at least two days in disney if you can, though I personally would do more! If you can't then make them midweek days when there are generally less people there. You can then spend time wandering around the shops and taking in a show etc on a day when you've done the must do rides.
There are much bigger rides at California Adventure, so check the height restrictions on your ds's before you go in. DOn't think that you can get away with being just a tiny bit under, they won't let your dc on if they aren't tall enough, simple as. So don't queue up thinking you'll get away with it, you won't. I saw one child in tears after queuing for ages who was then turned away. His dad knew he wasn't tall enough as he was measured at the start of the queue and chanced it. He was tthen turned away by the operator at the head of the queue.
There is lots they can do still though, like the amazing california screaming. And I really urge you to go on that ride. It has only one loop (if I had known that before I got on wouldn't have done it probably!) but so glad I did. Truly amazing experience with the music and speed you zoom off at...! Oh and the grizzly bear river ride, you will get wet but you will also dry off quickly. And of course the tower of terror. Fantastic, but pretty much the same as the paris one if you've done that before. Again, if you go in the squirt/splash park your dc's will have to wear shoes and keep their t-shirts on, so take a pair of flip flops in your backpack. You can always buy them a souvenir t-shirt if they get very wet, but they will dry fairly fast anyhow.
Must do rides in disnelyland - indiana jones, space mountain (fantastic and nothing like the awful version in paris!), splash mountain (very long queues here and fast passes go quickly), runaway mine train, oh and the pirates of the carribean in california is the best verion of the ride you can get. Lots of others too but these are the absolute must dos for my ds. The nemo ride is fine, but don't queue for it more than an hour I would say. It was newly opened last time we went and 2 hour minimum queues all day. Was fun but not worth a 2 hour queue.
My ds loves toontown area because he plays the disney toontown game and all the stuff like the trolley and donald's boat etc is there. So if your dc play toontown then they will want to go there. It closes early for the fireworks though. But if you don't have many days at the parks I would say you can skip toon town and most of fantasy land. But really you haven't done disney unless you've been on Dumbo, the teacups, seen mickey and minnie...
Do use the train which goes right around the perimiter of the park to get round to the far side. But first thing in the morning it's quicker to walk accross the park rather than wait for a train.
It does tend to be less busy in the week as visitors are mainly 'local' Americans. And you really notice the increase in visitors at the weekend. We've been at Easter and Halloween in the past and we still found the queues reasonable (with a couple of exceptions like the haunted house at Halloween). In fact I rememeber one evening when we stayed very late, and did the pirates of the carribean about 6 times in a row, getting off and running round to the start and getting right back on again!
Don't be afraid to ask for a front or back seat either. The staff are more than happy to oblige, but you may have to wait for the next ride.
disneyland.disney.go.com/disneyland/en_US/calendar/monthly/monthly?name=CalendarMonthlyPage&date=201 00818
Oh and we've stayed at different places when we've been. If you want a simple hotel room (inc breakfast) than I can recommend the Ramada Inn which is 2 mins walk across the road from the main entrance. It has an outdoor pool, you can see the fireworks (mostly) from there and plenty of parking. You can book it online too and they don't take the credit card payment till 24 hours before you get there.
We also stayed at Disney's Paradise Pier Hotel. It has a 'roof top' pool and excellent facilities. A lot more expensive than other places we've stayed, but the cheapest of the Disney hotels. My ds loved it so was wll worth moving hotels for a three extra days we spent there to make the holiday extra special. Would do that again if I had money to spare. However we did have to walk furtehr to get to the parks from there than we did from the Ramada!
The Grand California, which we went through to get to the parks, has an entrance straight into California Adventure park, and a mono rail to the other park. It looked very impressive, but we could still use it's pool and facilities as we were staying at the other disney hotel. In truth we didn't though.
The advantage of staying in a disney hotel is that you can get admittance to the park an hour early and so can get on some of the rides before they get busy. Do bear in mind though that some of the park area and rides do not open early so make sure you can get to the ride you want if you do go for an early start. If it's not open you will at least be friont of the queu when it does.
One last tip. Some rides have those auto photo things and want you to buy the photo. But on several (Like california screaming) you can simply use your own camera to take a picture of the screen shot. Saves you forking out for expensive photos!
You'll have a fab time, it's truly wonderful. If you need a disney guide I'll be happy to come with you in case you couldn't guess!