Hello Bonnie,
Our experience has been that naps were essential to a successful visit to WDW when our children were younger. Without a break, they could easily become pretty grumpy. Overall, the majority of the days we did return to the parks, especially to catch the parade and fireworks. However, we didn't do it every time and based our decision on our children's mood.
If you don't go back to the parks, there are often many things still happening around the resorts that can be enjoyed, such as movies by the main pool. Just stop by the lobby concierge desk to inquire about options.
As for the must-sees, I think you'll find the
Magical Beginnings Guide a helpful tool. Please keep in mind that ToonTown at the Magic Kingdom is no longer there and
Fantasyland is undergoing some renovations that will be open on December 6, 2012.
Thank you for the question; please let us know if we can help again.