Leslie,
WDW has some of the best accomodations for families with young children I have ever seen. Each park has a "Baby Center" but don't let the name fool you, they are designed for toddlers, too. In addition to the bright, clean changing area, there is also a small "dining room" with toddler size furniture and high chairs. There are some nice chairs for relaxing and fresh clean bathrooms. I think that there is a small toilet, but as DD was only 1 1/2 yo when we went we didn't really look. In each Baby center, there is also a wide variety of products to purchase, from diapers and wipes to food and juice. Look for the centers by the First Aid stations. In MK, it is right next to the Crystal Palace. In Epcot, it is between the World Showcase and Future World and in MGM, it is near the entrance. Have a great time!