Hi Angela! The three parks I would choose would be the Magic Kingdom, Hollywood Studios, and Animal Kingdom. This would give you a taste of three of the four parks during your Florida visit.
I would suggest you hit the Magic Kingdom on the 20, 21, 22, or 25. I am not sure if the 20 and 25 are travel days so it is hard to plan the exact itinerary. Those are days that the park does not have the Extra Magic Hours which are open for resort guests to stay later or arrive earlier. The parks on those days tend to be busier as guests want the most hours for the cost of their ticket.
Animal Kingdom park would be good on the 21, 23, 24, or 25. Hollywood Studios looks best on the 21, 22, 23, and 24.
If the 20th is your arrival day I would not use it in a park. On the 21 I would head to the Animal Kingdom park, then on the 22 go to the Magic Kingdom, and then skip a day and head back to Hollywood Studios on the 24th. There are plenty of attractions in each park that the girls will enjoy or can do together. Although their experience will be different due to the ages you can still have fun as a family. Check out the list of perfect attractions for pre-schoolers at the Disney site.
http://disneyworld.disney.go.com/attractions/