My understanding is that Disneyland still operates on the paper Fastpass system, so that hasn't changed (unlike in Orlando), and that the highest priority Fastpass is the Radiator Springs Racers one, where lines are massive. And remember that some attractions are quite different in California and Florida--the California Pirates is twice as long, for instance.
Yes, you must get the fastpass for Radiator Springs first thing if you intend to ride that ride. If the kids are old enough, you can do single rider,which gets you onto the ride pretty quick. Soarin' over California is awesome. If it's warm, do the rapids. For Disneyland, working the fastpass always helps. Get one for Space Mtn, autopia, Indiana Jones. And my family loves the corndogs at the end of Main St. Have fun!
Buy a 3-month subscription to RideMax and plan your visit, including where you're going to eat. RideMax will tell you which rides to get FastPasses for and which you can just wait for.Magic Kingdom in California is so much easier to navigate than MK in FL, and you can literally walk between parks. Grizzly River Rapids is infinitely better than the Kali Rapids ride at Animal Kingdom in FL. Perhaps the best thing is that, with planning, you can spend 2 days at DisneyLand and not feel as if it was a waste of time. 2 days in Florida and you'd be missing a lot, but 2 days in California and you can be satisfied if you do it right.If your kids are into meeting the princesses, get fastpasses or talk them out of it -- that was the biggest time-waster we saw at our recent trip to DisneyWorld. I can't imagine spending so much on park tickets and then waiting 3+ hours just to spend 45 seconds with a cast member in costume. The lines in Norway to see Anna and Elsa were insane.
Ditto everyone else on Radiator Springs Races--if you are staying at a Disney Hotel, try to get into CA Adventure during early magic hours and go straight to RSRs. Definitely get park hopper passes--the two parks are so close and you will want to cross over between the two. In general, food at the California parks are MUCH better than Orlando. CA Adventure has a nice food court area in the faux Fisherman's Wharf section. I am partial to all the Disneyland "original" rides--ones that only exist in CA or are better than their WDW counterparts---Small World, Indiana Jones, Mattahorn, RSRs. World of Color is really worth it, and Disneyland's version of Fantasmic is better than Orlando's.
Everyone said what I came here to say re: Radiator Springs, Soarin' (so cool!), the park hopper passes (worth it), and World of Color. I usually think water/light shows are a snooze, but WoC is really impressive. If you make a reservation for dinner at the fancier restaurant (blanking on the name, it's not SUPER upscale, just upscale for a theme park) at CA Adventure you get priority seating for WoC and it's totally worth it. Have so much fun!!
Do the CA big coaster before lunch, but well, well after breakfast. Puketastic!
And plan something loud and exciting immediately after It's a Small World to dislodge that infernal song from your head.
SO. MUCH. SUNSCREEN. (But you already knew that.)
I've only been to the Florida park once, I've been to the CA parks more times than I can count. I'll add my love for Soaring over California. I generally dislike heights or scary rides, and Soaring is AWESOME. I'll ride it over and over. The classic rides at Disneyland are great - teacups, small world, pirates, haunted house, dumbo. My 10-year-old son (surprisingly) loved the Davey Crockett canoe "ride." The Toy Story Buzz Lightyear Astro Blasters ride is another one we went on over and over. And have a churro!