Visit the official Disneyland website, with your preschooler. Click on
"Attractions and Entertainment" so your child can look at the rides. Note the height limitations the rides, and look for indications that the more intense rides such as the Matterhorn may be too frightening for your preschooler.
Measure your child's height so that you know which rides to avoid. You'll head off any disapointment.
Plan your day. You'll probably spend most of your time in Mickey's Toontown or Fantasyland where most of the kids' rides are. Find out where the bathrooms, snacks and first aid stations are in case you need to find them in a hurry.
Consider going during the off season or during the week, when the crowds are thinner. You don't want your preschooler getting wiggly standing in long lines. If you go during the off season, not only will the lines be shorter, but it will probably be cooler, so your child won't be in danger of baking in the Los Angles sun. Going to Disneyland off season or during the week also cost less.
Think about going to Disneyland for more than one day. This will allow your child the time to go on rides they like repeatedly and will give you time for breaks. You'll see more of Disneyland this way.
Rent a stroller on Main Street if your preschooler's energy wanes.
Bring your preschooler's favorite snacks and drinks. Not only will this be cheaper, but your preschooler will have their favorite foods. You won't track down snacks to please a finicky appetite.
Remember, Los Angeles can be torrid during the summer. Bring appropriate clothing, make your child wear sunblock and a hat and sure they drink plenty of fluids.
Take breaks. Consider leaving the park in the middle of the day to go back to your hotel room for naps or some other restful activity. A nap may prevent your child from wearing down. If you can't leave the park, plan on seeing some shows at mid-day. You also could enjoy long sit-down attractions like the Tiki Room, the Jungle Cruise, Small World, Mark Twain Riverboat, Pirates of the Caribbean and the Disneyland Railroad.
Use the fast-passes. Many popular rides offer fast passes that allow you to "cut" in line at specific times.