We'll be there during that time as well. Here are my suggestions.
MGM is a MUST for your kids. It has TOT, RNR, Star Tours, WWTBAM and lots of other stuff. Plan on an entire day here.
Epcot is also a must. Test Track, Soarin and Mission Space will send the kids into thrill overload...an entire day here as well.
on an off note, I would STRONGLY suggest going to a water park.
We personally like Typhoon Lagoon, but maybe BB would be a better choice for that age group (Summit Plummet). That may sound weird, but the water parks are more popular to my kids, and they're little, than most of the theme parks.
Magic Kingdom is a must do, even if just for a little while. It has Space Mtn, Splash Mtn and BMR, but the magic is there. It is Disney.
Forgot that Expedition Everest will be open, so I would plan a half day here to do that and Dinosaur.
I would avoid MK on Saturday and Epcot on Sunday..just my personal experience. If you can do them mid-week, should be a little less crowded.
Hope that helps. Have fun, we will!!!
