Hi Cathy:
I've been traveling to Disney World with my boys, ages 8 and 6, since they were infants. Watching them "grow" into certain rides has been a fun experience.
A number of Disney World attractions are restricted by height. I would play around a bit on
Disney World's attractions page and use the filters to help prioritize attractions and rides by height and age interest. A number of attractions at Magic Kingdom and Epcot may be off limits for now based on your boys' height, so that should help narrow down your choices. For example, your family likely will not be able to ride Big Thunder Mountain, Space Mountain, Splash Mountain, Test Track, and Stitches Great Escape. Although I love old favorites, such as Carousel of Progress, Hall of Presidents, Swiss Family Treehouse, and Maelstrom your boys may not enjoy them.
You will have fun weather you can spend hours or days at either Park. My best advice is to relax and follow your boys' pace.