Hey there, Tiffany! Thanks for stopping by to see us again at the Disney Parks Moms Panel. Sounds like your little guys have some big plans for your upcoming Walt Disney World trip!
What a milestone it is when your kids are finally tall enough to take on some of the thrill rides in the Theme Parks. I'm not sure who gets more excited, the kids or the parents. Our son recently overcame his fears of riding the "fast rides," as he calls them, and suddenly he's become a little daredevil!
Height requirements can vary by attraction, so each one with a restriction has its own measuring stick, often right near the ride entrance. The Cast Members are very good at spotting which young Guests are close enough to the required height to need a measurement and will ask you to pause while they check. If your sons are tall enough for the "bigger" rides like Space Mountain or Big Thunder Mountain Railroad, you probably won't be asked for a measurement for attractions that have shorter requirements, such as the Seven Dwarfs Mine Train.
The Disney Parks Blog created this fun chart with the height requirements for all of the attractions at the Magic Kingdom Park. In the article, you'll find links to similar charts for the other Theme Parks, too.
I hope this helps you and your little thrill riders have a blast on your vacation, Tiffany. Please visit us again if you have any more questions.
Keep Disney Dreaming,
Kathy K.