Hi Brandi,
Welcome to the Disney Parks Moms Panel! What perfect ages your kids are for a trip to the Walt Disney World Resort! When we took our girls at 5-years old, they thought everything was REAL - the wonder in their eyes was just priceless!
If you have to choose between the parks, I suggest that you prioritize in this order - Magic Kingdom, Disney's Hollywood Studios, Disney's Animal Kingdom and Epcot. That prioritization, however, really depends on the interests of your children.
Magic Kingdom attractions are amazing for little ones. There are quite a few that are appropriate for kids of any age - some of my girls' favorites have been The Barnstormer, Astro Orbiter, Seven Dwarfs Mine Train, Big Thunder Mountain Railroad and Pirates of the Caribbean. Disney's Festival of Fantasy Parade, the Move It! Shake It! Dance & Play It! Street Party and the Happily Ever After Fireworks are also spectacular.
Honestly, either Disney's Hollywood Studios or Disney's Animal Kingdom theme parks would be a great second choice. Our girls love Disney's Hollywood Studios because they feel called to defend the galaxy in
Jedi Training - Trials of the Temple. They really believe they can wield the Force and defeat the Dark Side. After training, we always go ride Star Tours - The Adventures Continue. We visit Star Wars Launch Bay and then ride Toy Story Mania! At Disney's Animal Kingdom, however, the animals are AMAZING. And with expeditions departing every day to Pandoroa - The World of Avatar, your adventure awaits.
Brandi, time is essential! If you have not purchased park tickets, do so as soon as possible so that you can make your Fast Pass+ selections.
As we say on Pandora - Sivako! Rise to the Challenge!
Donyell