Hi Kennon,
We're so happy that you could visit us here at the Moms Panel, and ask your awesome question. When it comes to listing the best attractions for a 3 year old and 5 year old, we could go on for days! With 4 theme parks to explore, it's quite difficult to narrow them down. I have a 4 year old, so I can at least list the attractions that she loves to visit when we vacation at Walt Disney World.
In Magic Kingdom, the options are endless when it comes to attractions for 3 and 5 year olds. Most of the park is geared towards providing experiences that the whole family can enjoy. Our 4 year old princess loved Splash Mountain,
The Barnstormer, and Peter Pan's Flight. Keep in mind that there is a height requirement for certain attractions, so you may want to measure the kids before you arrive to make sure they can ride select attractions.
When we visit Disney's Hollywood Studios, we are all about Toy Story Mania. This attraction is made for families with young ones, and it's one that parents won't mind riding over and over again.
For more attraction options for Magic Kingdom, Hollywood Studios and the other theme parks, check out this page:
Planning for Pre-School Kids & Little Ones. The downloadable guide will not only help you decide with attractions will be best for your 3 and 5 year old, but you'll learn some great tips and tricks for maneuvering the parks with little ones.
I hope this answer helps you, Kennon. If you have any other questions, feel free to ask us at any time.
Have a fantastical Disney day!