Hey Howdy Hey, Angela!
You've got a friend in me here at the Disney Parks Moms Panel, so thanks for your great question. Your son sounds a lot like my little one when he was 2. He has always been so fascinated by the Cars films and vehicles and loves Buzz and Woody!
Disney California Adventure Park is definitely your location for all things Cars as well as a lot of Pixar and Toy Story attractions and Characters. Cars Land is a dream come true for fans of these films as you can walk right down Route 66 and feel like you are immersed in Radiator Springs. There are three attractions in this land, two of which have a 32" height requirement and one with a 40" height requirement. Plus you can also meet some of your favorite Cars Characters like Lightning McQueen and Tow Mater. In
Pixar Pier of Disney California Adventure Park you can ride Toy Story Midway Mania, Jessie's Critter Carousel, and see many Pixar Characters on Pixar Pal-A-Round. Here is where you can also meet famous Characters from Toy Story films like Woody, Buzz, Jessie, or Bo Peep.
While Disney California Adventure Park has more of your son's favorite Characters, Disneyland Park definitely packs more attractions that are family-friendly and perfect for little ones like your son. He will love classics like "it's a small world," Peter Pan's Flight, Pirates of the Caribbean, and Dumbo the Flying Elephant to name just a few. Because of this, I really think your best option with a one-day ticket is to purchase a
Park Hopper ticket. This will allow you access to both parks throughout the day so you won't miss out on anything. It's so simple to walk between parks. We do it every time we visit!
I hope this helps, and please return if you have any other questions. See ya real soon!
-Jennifer