We stayed at MGV in early May with a 3 1/2 year old and a 1 year old and found that mid-day breaks worked well for us. We would typically head for the parks to be there in time for opening (no problem as the kids are early risers), eat lunch no later than noon, hit a couple more attractions and head back to the villa around 2 for naps/swim. We'd usually head back to the parks (sometimes eating an early dinner first, sometimes just snacking at the park) around 6 which got us there in time for evening shows.
One tip is to take International Dr. south taking a right at the last light where you have to turn. Not sure what this road is called (World Center Dr. maybe?) but it brings you out right at the huge Orlando World Marriott complex where you can jump on the Disney roads (just follow the signs). We found this to be faster than taking I-4. One night we stayed for Spectro and Wishes and left right at park closing and the MK was packed but we were back in our condo 45 minutes after the fireworks ended, exiting, monorail, tram and drive included.