Welcome to planDisney, Angela.
As a fellow Walt Disney World Resort regular, I'm so excited to hear you'll be visiting the Disneyland Resort. I know you'll find it to be equally magical. Here are my personal recommendations for you:
Attractions/Shows
I'm going to give you a long list here. However, if you purchase
Disney Genie+ and get to the parks at opening you should have no problem experiencing most of these. I've tried to emphasize attractions that are unique or different from what you'll find at the Walt Disney World Resort.
At
Disneyland Park, you obviously have to do the classics, Mr. Toad's Wild Ride, Pirates of the Caribbean (far superior to the Magic Kingdom Park version), Alice in Wonderland, Autopia, Casey Jr. Circus Train, "it's a small world," Sleeping Beauty Castle Walkthrough, and, of course, the Disneyland Railroad. I'd also recommend taking advantage of Rider Switch and riding Matterhorn Bobsleds, Space Mountain (again, I think superior to the Magic Kingdom Park version), and Indiana Jones Adventure.
Also, make sure you watch
Fantasmic! (it's slightly different than the show you'll see at Disney's Hollywood Studios),
Wondrous Journeys, and the
"Magic Happens" Parade.
At
Disney California Adventure Park, I'd suggest riding Luigi's Rollickin' Roadsters, Mater's Junkyard Jamboree, WEB-SLINGERS: A Spider-Man Adventure, and take your 4-year-old on the Redwood Creek Challenge Trail (my kids love it so much). I'd also recommend taking advantage of Rider Switch and riding Guardians of the Galaxy - Mission: BREAKOUT!, Incredicoaster, Radiator Springs Racers, and Grizzly River Run.
Finally, if you're in Cars Land when it first goes dark you can enjoy something special. But you might prefer to find a good spot to watch
World of Color - ONE.
Dining
Disneyland Resort has many fantastic dining options; too many to experience all in one trip. However, let me offer the following suggestions. At Disneyland Park, try and get a reservation for Blue Bayou Restaurant. A good quick-service option would be Bengal Barbecue.
At Disney California Adventure Park, I'd recommend getting a reservation for Lamplight Lounge. However, if you want to do something extra special, see if you can get a reservation for Carthay Circle. A good quick-service option would be Flo's V8 Cafe or Pym Test Kitchen.
I hope that's helpful, Angela. There is a lot for you to do! However, I trust you'll absolutely adore the Disneyland Resort. It truly is The Happiest Place on Earth.
Mike