Another vote for Epcot! We are planning another trip for November, to bring my in-laws. They went with my husband's sister and her family (3.5 and 5.5 year old kids) last April, and NEVER went to Epcot since my SIL thought the kids would be bored!
My kids, 6, 13, 14 all love Epcot!! In fact, it is my 6 year old's favorite park, even though her favorite ride's are all the thrill rides. Future World has lots of fun, if slow paced, rides and shows, and they all exit into play areas with fun things to do! Even more of a plus, they are all in pavilions, so they are air-conditioned in the heat!
When my youngest was 5, she spent two full days in Epcot, from opening till closing - and still didn't have enough!! Of course, she loved the Tapestry of Dreams parade, which no longer exists, but she loves all the street entertainment in the World Showcase, and the mask making at the Kidcot stations occupied her for hours!! The one thing we did on our first trip that we won't bother with again is buying the Passports - they were expensive, about $10 each times 3 kids - and the kids just didn't get into them that much. They much preferred the masks, which were free, and make a colorful - and depending on your kid's artistic ability - beautiful souvenir. They are hanging on the girls' bedroom walls still! The CM's will stamp the stick of the mask, just like the passports, and several of them also wrote little notes in their native languages. They also showed my daughter how to write Sarah in Chinese!
We do
rent a stroller in Epcot, although since she will be 7 in November - we may not this time. This saves any whining - because there is so much to see, even from the stroller point of view.
MGM, on the other hand, is not a hit with her! Even though she is now tall enough for Rock N Roller Coaster, her favorite ride!, as soon as she rides it once -- she starts begging to go back to the resort to swim! Even though they have plenty of kid oriented shows, restaurants, etc. The general atmosphere of this park just turns her right off!