Hi Gwen!
Our boys LOVE, LOVE, LOVE Magic Kingdom, Disney's Hollywood Studios, Epcot, AND Disney's Animal Kingdom, so make sure that you visit all four parks!!
When I budget for time, I generally allow 2 days for Magic Kingdom, 2 for Epcot a day and a half for Disney's Hollywood Studios and a day for Disney's Animal Kingdom. It also depends on what your boys preferences are, and the time of year you are visiting. You'll be going at a generally lower attendance time of year, so crowds should not be a huge factor in your touring plans.
I know from our experience that we will spend a good portion of time at Magic Kingdom and Epcot. I also know that we will re-visit Disney's Hollywood Studios at least 3 times during our trip, but we park hop, so that makes a difference as well.
Make sure you go through the attractions with your boys (on the
Disney Parks DVD) and take note of what they are interested in--then you can plot that information out and see just how many attractions they are looking forward to in each park. It'll show you where you'll be spending most of your time.
Have a magical vacation!
Amanda