My boys are the same age as yours...in addition to the ones mentioned:
EPCOT:
Soarin'
Living on the Land (they LOVE this)
Turtle Talk with Crush
Innoventions exhibits...they loved the recycling one where you push the recycling truck around and sort the garbage and such.
Spaceship Earth (they ride this several times, usually)
AK:
The safari ride...we usually go on this and get a fast pass for later, as well.
The gorillas (I think they're on the Pagani Trail)
The parade
MK:
-Splash Mountain (if they like water rides...they WILL get wet. I have one that really loves this ride and one that hates it.)

-A second mention for the Tomorrowland Speedway. They LOVE this.
-Tea cups
-One of mine had always wanted to ride the horse pulled carriage down Main Street, so we did that last time. They thought it was really fun. It meets in front of the train depot.
HS:
-the stunt shows are huge hits
-A second for Toy Story Mania...head over there first thing in the morning though. If you get on right away, make sure that you grab fp's for later. They will love this ride.
DTD:
-the
Lego store is a lot of fun...they have a building area outside. And they have some amazing and enormous creations.
-there is a car building store somewhere down there if they/you are into that thing. It's kind of like Build a Bear for cars. Avoid it if you don't want to spend the cash though.

I don't think it's in the Marketplace, so it's easy to avoid. We've actually never been there for that reason, but I've seen lots of little boys carrying the boxes around. They were really excited about them.
-World of Disney...has pirate stuff and lots of souveneirs. They love going there and picking something out.
-Pin Traders (I think that's what it's called.) My eight-year-old really got into the pin thing this year...the six-year-old thought they were fun, too. They didn't trade, but they like using their money to pick them out as souveneirs. This store has a really good selection.
Have a great trip!