Company's that have conferences in the area often offer 2 or 3 day park hoppers to attendees and their familes. If offered, the 3 day would probably be even cheaper than two one day passes if purchased separately.
If you can hop, bring a double stroller for the little ones and have fun. I would go to AK on friday morning and do the safari and the lion king show, meet the characters, maybe the pocahontas show and view the animals on the two trails. then after lunch head to MGM and catch a few shows where the little one can nap too. They would love Playhouse Disney live, Beauty and the Beast, Voyage of the Little Mermaid, and then they can run off energy in the honey i shrunk the audience playground adventure. watch the parade at 5pm and head back to the hotel.
then on Saturday, start the day at the MK. Hit Fantasyland and Toontown, then the jungle Cruise and Tiki Room and have lunch. Then catch the monorail over to Epcot (transfer at the TTC) and visit the Living Seas, Ellens Energy adventure (baby can have a nice nap in this 45 min ride/show- it is dark and air conditioned), and spaceship earth. Then head into the world showcase hitting mexico first. let the kids have a treat from the Norway bakery, and just walk through the pavillions, perhaps stopping at the kidcot stations or to visit the characters in their native countries. Have dinner at a counter service in the World showcase and grab a spot for illuminations about 45 min before 9pm- bring coloring books or a small new toy to entertain.
Because the weather is unpredictable be sure to keep sweatshirts in the stroller.
I think this would be a great visit and I am a mother of 4 girls under age 8 so i know it seems daunting. I will be there at the same times and the crowds should be low at those parks on those days. Good luck and have fun!