Hello, Adele! Thanks for stopping by the Disney Parks Moms Panel and asking your question!
Taking little ones to the Disneyland Resort is tons of fun, so you will be making lifelong memories all day. While I think that it's definitely possible to experience both parks in one day, you would only be hitting a few of your must do attractions. If you want to offer a fuller experience, I recommend focusing on just Disneyland Park if you only have one day to visit. This way you can take your time and really enjoy all the wondrous things Walt Disney's original park has to offer - especially for little ones.
You could first ride attractions like "it's a small world," Dumbo the Flying Elephant, Storybook Land Canal Boats, and Buzz Lightyear Astro Blasters. Then, perhaps after a tasty churro or some fresh fruit, you can let them explore all the fun in Mickey's Toontown. Goofy's Playhouse and Donald's Boat are favorites of my 4-year-old, as are meeting Mickey and Minnie and walking through their houses.
For lunch, venture over to French Market Restaurant or Hungry Bear Restaurant. Hungry Bear even has some really nice tranquil seating options that overlook the Rivers of America. Then you can jump on The Many Adventures of Winnie the Pooh, Haunted Mansion, and Pirates of the Caribbean. If your kids still have some energy to burn, take a raft over to the
Pirate's Lair on Tom Sawyer Island.
Then your day could continue with
Mickey's Soundsational Parade, meeting more characters, seeing Mickey and the Magical Map, or just relaxing on the Disneyland Railroad or Mark Twain Riverboat. There is so much to see and do that you will definitely have a full day of fun at just one park. Have a fabulous visit!
-Linda M.