Plan on less is more.
In MK all we did was CRT, IASM, Belle's story time, got a Mickey hat, ate some Mickey bars, played in ToonTown, rode the train, and watched the parade. Oh and we slept in Country Bears Jamboree. We spent tons of time running through the rose garden, changing dialers in the Baby Care centers, and finding cool spots to sit for a minute and let the wee ones out of the strollers.
In Epcot we did the WSC, but I gotta tell you, this was too much. We rushed through each country and played a little in Italy and Japan, but that was it - it was a speed marathon punctuated by trying to find the best restrooms for changing - having both mothers not on the same changing schedule really screws up your day so try and coodinate the changing routines - but sometimes this just isn't possible. We should have not done so much and stayed longer in Living Seas which the wee ones loved. Same story for MGM - we tried to do too much in the heat.