Hi Spring:
I have a five and a three year old who love visiting Walt Disney World. There is so much to do at Disney that if you can swing four days instead of three, I would. However, you and your daughters are sure to have a wonderful and memorable experience even if your trip is three days.
A four day trip will allow you to spend quality time at each of the four theme parks at Disney World; Magic Kingdom, Epcot, Hollywood Studios, and Animal Kingdom. As for the theme park that may be best for your daughters, that would depend on your daughters' interests. But as a basic rule, my family never goes wrong with the Magic Kingdom where we enjoy, among other attractions, Dumbo the Flying Elephant, it's a small world, Jungle Cruise, Mickey's PhilharMagic, Peter Pan's Flight, The Many Adventures of Winnie the Pooh, Pirate's of the Caribbean, Tomorrowland Transit Authority People Mover, Haunted Mansion, and Monster's, Inc. Laugh Floor. At Magic Kingdom, your daughters can also become princesses at
Bibbidi Bobbidi Boutique, or dine in a castle at
Cinderella's Royal Table (don't forget to make Advance Dining Reservations up to 180 days in advance).
If your daughters love animals, make sure you make a visit to Animal Kingdom. If they like movies and television, visit Hollywood Studios. However, if you think your daughters would not like either of those parks, then I would spend more than one day at Magic Kingdom.
Enjoy your visit.