Hello there Courtney!
I love the Contemporary Resort! In fact, I think I may be staying there on my next trip! Your question needs to be answered in four parts since each Theme Park has their own great play area.
Magic Kingdom has three mountains which your younger one will not be able to ride but there are great options for you. If the lines aren't too long, there is a small play area in between Splash Mountain and Thunder Mountain which the kids could play. Over by Space Mountain, you could take a ride on the Tomorrowland Transit Authority PeopleMover. The kids will love it!
Epcot has a few rides which your younger ones may not be able to go on. My advice would be to go to Innoventions and see all of the hands on exhibits.
Hollywood Studios has the Honey I shrunk the kids play area which would be lots of fun for the little ones or head over to “Disney Junior - Live on Stage!” will the big kids ride Rock-n-Roller Coaster or Hollywood Tower of Terror!
Animal Kingdom also has a very large play area near the Dinosaur ride called The Boneyard or you could walk through some of the animal exhibits.
I hope this information helps you with your planning and if you have more questions, please ask away, we are always here to help! Have a Magical Time at the Walt Disney World Resort! Thanks so much for asking the Moms Panel!