Hi Kristen!
I have two boys, ages 12 and 7. When they were younger, they both loved the Magic Kingdom, the Future World portion of Epcot, and Disney's Hollywood Studios. They both also enjoyed Disney's Animal Kingdom, but they liked the other three parks better. At 4, the Magic Kingdom was their favorite park.
All of the parks have attractions and shows suitable for the whole family. The Magic Kingdom has the most, but there are plenty of attractions in the other parks for a whole day visit. My recommendation would be:
- Day 1: Magic Kingdom
- Day 2: Future World portion of Epcot
- Day 3: Disney's Hollywood Studios
If you have an extra day at the end, then you could go back to your favorite park, which will most likely be the Magic Kingdom. But if you saw everything you wanted to see in the Magic Kingdom, then you could visit Disney's Animal Kingdom on that last day.
By the way, Epcot is divided into two parts: Future World and World Showcase. Most young children don't enjoy (or at least don't love) visiting the World Showcase portion of the park which is where the country pavilions are; that's too bad, because that is the favorite section of most adults. However, there are a lot of attractions in Future World that your 4 year old will probably enjoy, especially in the Seas with Nemo and Friends pavilion. When my youngest son was 4, he could spend at least half a day in that pavilion!
I hope this helps! Write back if you have any more questions!