Hi Ryan!
First, congratulations on your sons' 1st visit to Disney World! 4 to 5 is a perfect age to bring them. They're old enough to understand where they're at, but not too old to experience the magic as only a 5 year old truly can.
My son is still a pre-schooler and my daughter left the pre-school era a couple years ago (about to turn 7-which has me wanting to kick, cry, and scream like...a 5 year old. My baby's growing up) :-(
At pre-school age, my kids never really like rides with long periods of darkness, have loud noises, or hidden surprises. The rides that "tanked," in terms of my kids were:
Stitch's Great Escape (Magic Kingdom)-long periods of darkness, loud noises, Stitch's laugh coming through the speakers behind you. Cool for me but my kids were totally NOT OK with it...
Spaceship Earth (Epcot)-slow moving ride, but the long periods of darkness really freaked my son out.
It's Tough to be a Bug (Animal Kingdom)-3D experience, periods of darkness, too scary for both my children...yikes!
Muppet Vision 3-D (Hollywood Studios)-apparently my children don't like the 3D thing. Another attraction that didn't go too well at the less-than-5 age.
Perhaps your sons will have a totally different experience, but these are one's to keep on your "not-so-sure" list.
May you and the family have a terrific time!