Hi, Megan!
Welcome to the Disney Parks Moms Panel, and thanks for your great question. I bet your family is looking forward to the magical vacation ahead this summer!
I took my own 3-year-old son to the Walt Disney World Resort last fall. We spent the most time in Magic Kingdom Park, but Epcot is so large with so many different restaurants, experiences and attractions for the whole family that we actually spent quite a bit of time there, as well. Disney’s Animal Kingdom Park has fewer overall attractions and closes much earlier than all the other theme parks, so in my opinion, it would be a better choice for a half-day than Epcot. I recommend checking out the online attractions list for Disney's Hollywood Studios so you can map out your family's must-do attractions and budget time accordingly.
If you’re deciding whether to spend three or four days exploring the resort, I would definitely plan to visit for four if that’s feasible so you have time to experience much of what all four parks have to offer while still building in time for naps and breaks. With a little one in tow, some downtime and rest is necessary for an overall great experience for everyone, especially in the warm summer months.
I hope this helps, Megan, and that your family enjoys a perfectly pixie-dusted vacation. Please visit us again with any other questions you have.
Wishing you magic,
Courtney