Hi Jackie! One of the wonderful things about Walt Disney World is that the vast majority of attractions in the parks can be enjoyed by guests of all ages and sizes. In each of the four main parks, there are only a few rides with height restrictions. In general, if your children are 48 inches tall, they'll be able to ride everything; if they're at least 44 inches tall, they could ride every ride in the four parks except for two roller coasters.
Here are the attractions in each park that have the tallest height requirements: At the Magic Kingdom, Space Mountain has a 44" minimum height requirement, and to drive one of the cars on the Tomorrowland Speedway, the guest must be 54" tall. (However, smaller children can ride in a speedway car with a taller driver.) At Epcot, Mission Space requires riders to be 44" tall. At Hollywood Studios, the Rock 'n' Roller Coaster has a 48" height requirement. Finally, at Animal Kingdom, Expedition Everest requires riders to be 44" tall and Primeval Whirl has a 48" minimum height.
You can review all the height requirements by clicking
here, and downloading the "Attraction Height Requirements" file on the right side of the page.
Hope this helps! Feel free to visit us again at the Moms Panel if you have further questions!