I helps to have a loose plan, which you can casually follow according to you and your child's mood. Plan to arrive early, and allow for rest at your resort in the afternoon. Take it slow, without expectations to see it all, and enjoy every moment.
In general, we will go on several rides, say in Fantasyland and Mickey's Toontown, until lunch at a location where we have PS. After lunch we head to our resort for a swim and rest, before getting ready for an early dinner at 6pm. We check the entetainment schedule to see if there are any parades or events early enough in the evening for the little ones to enjoy. The whole family usually passes out earlier than usual at the end of the day.