At California Adventure FP isn't really needed as much as it is
Disneyland.
If you can experience most of the attractions before 10am-1030am, you'll be good for the rest of the day.
For the park opening at 8am example, Avoid Cars Land all together and head straight to Paradise Pier and do Toy Story Mania, then Screamin, Fun Wheel, and Goofy Sky School.
Mermaid , Symphony Swings, Zephyr, and Jellyfish can all be done later in the day with very low waits.
Get on Soarin by 9am-930am then Grizzly by 930am-10am.
Now grab that FP for Radiator Springs Racers then visit Bugs Land and Tower or Terror between 1030-1130am
Before lunch grab a disconnected FP for Anna and Elsa, then eat lunch early.
After Lunch Grab a FP for Frozen Sing a Long and just stay around Hollywood land until you meet Anna and Elsa, see the Sing a Long, visit the snow, ride Monsters Inc, and perhaps see Aladdin.
That should all end at around 2pm-3pm and you can then rest back at the hotel or do the things you missed so far.
Once you get back you can do all of the Cars Land attractions.
At Disneyland you just have to remember to grab your next FP before you use your current FP.
8am-9am: I would do Fantasyland Stuff. First Peter Pan, then Dumbo, Alice,
Mr. Toad, Casey Jr., then single rider Matterhorn. Snow White, Pinocchio, Storybookland, Mad tea Party can all be done later.
9am you want to head to the Westside (Adventureland, Frontierland, etc...) of the park. You want to save the Tomorrowland side because the main attractions there have FP.
9am-1130am: Grab that FP for Indiana Jones, ride Jungle Cruise, ride Splash, Mansion, grab FP for Thunder, use FP for Indy, ride Pirates (might be a long line but it will move fast), Tarzan Treehouse, Grab FP for Space Mtn, and use FP for Thunder,
1130am-4pm Then have Lunch. After Lunch take the Twain, or visit Sawyer Island, Grab FP for Star Tours, use FP for Space, Buzz (might be a long line but it will move fast). Nemo Submarines or take a trip on the train around the park, Grab FP for Autopia, use FP for Star Tours, ride an attraction in Tomorrowland that you missed. then grab a FP on an attraction you want to do again.
Space and Indy are the most popular. With Splash being popular if the weather is warm. Star Tours is next, with Thunder almost lasting the entire day.
After all that you want to do Toontown and Its a Small World (non Holiday) as it tends to have lower crowds at around 5ishpm