Don't drive! By the time you walk to your car and then walk from your car to the tram, you'll have walked just as far as if you had just walked to the park from the hotel to begin with!
Most children enjoy the boat transportation and as Mic said, you can roll a stroller on - no emptying out the basket and folding it up!
EPCOT - If you children enjoy the characters, give the Garden Grill in the Land Pavillion a try. They serve lunch, dinner and in the afternoons they offer an "Ice Cream Social". Don't miss the Tapestry of Dreams Parade. Believe the kids can stop at one of the country pavillions inWorld Showcase to make "dreams" that are collected during this parade.
MGM - Be sure to check out the "Muppets 3D" attraction and the "Honey, I Shrunk the Kids Playground" and the new parade. "The Little Mermaid" attraction as well as the Beauty and the Beast show are popular with young children, as is the new "Playhouse" attraction (with Bear in the Big BLue House and Rollie Polie Olie).
Enjoy your trip!