Hi Teri,
When our children were younger, we took advantage of the parks when they opened or even Extra Magic Hours (are you a Disney resort guest?). We particularly liked (and still do this!) the Extra Magic Hours at the Magic Kingdom because we could do nearly all of Fantasyland within the first couple of hours. Being at the parks when they open is a terrific time to enjoy many attractions without the large crowds and lines. Make sure and utilize fast passes, too! However, if you don't have the park hopper option on your tickets, I'd avoid the Extra Magic Hours in the am since you can't switch parks.
By lunch as the parks became more crowded, we either ate at the park or returned to our resort to eat followed by naps & often a swim. By late afternoon or early evening, we would return to the parks (at this point I'd avoid any park with Extra Magic Hours -- morning or evening -- because of the crowds).
Overall, while we had this plan, we let our children's temperament determine the day. Sometimes simply have a one hour break was all they needed. Othertimes, it was much more. Traveling with a grumpy child can be pretty miserable, so our goal was to stay rested and hydrated knowing we would just try to enjoy our time rather than experience every single attraction. If you click
here, you will find a map & information on traveling with children under 5 that should be helpful (however, Toontown is now closed at the Magic Kingdom.
Have a magical trip!