Hi Amber,
Welcome to the Moms Panel, we're so glad you stopped by to ask a question! I know your kids (as well as you) are going to have a magical time in Walt Disney World. Your kids are at that age where their eyes will be filled with wonder and delight as they take in all of the pixie-dusted fun!
I do think they will most enjoy the Magic Kingdom at their ages, so I would think your plan to spend two days there would be a great plan. I would also highly recommend Animal Kingdom since many kids that age are really into seeing all the animals. Be sure to take them to the
Affection Section at Rafiki's Planet Watch, it is a favorite for my kids. My next suggestion would be Hollywood Studios since the
Disney Junior - Live on Stage show and
Toy Story Mania are huge hits with the younger kids.
This leaves off Epcot, and while it does have fun attractions like Turtle Talk with Crush and Journey into Imagination that appeal to little ones, I think they would get more out of the other three parks. Epcot is one of the largest parks with lots of ground to cover which can be hard on those tired tiny feet!
If you decide to add on the park hopper option where you can do just that - hop from one park to the next on the same day, you can do so even after you check-in by seeing a cast member in guest services.
May you enjoy watching your kids marvel at the sights and sounds of this happy place. Those memories are some of my most cherished.
~Allison L