Hi Shayna,
Trips with large groups can be so much fun!
You might want to choose
Disney's Animal Kingdom if you have lots of people in your group who are interested in animals. There are many unique animal experiences at this park, from viewing animals on a safari vehicle on Kilimanjaro Safaris to taking in animals such as gorillas on Pangani Forest Exploration Trail. If the rest of your party wants to ride a more thrilling ride such as Expedition Everest - Legend of the Forbidden Mountain, you or another adult from your party could take your little one on a ride on the Wildlife Express Train. This will take you out to Rafiki's Planet Watch. When my daughter was a toddler, she loved the Affection Section there, where she got to pet animals.
Epcot is a truly amazing theme park. From the excitement of Future World to the amazing diversity of World Showcase, there is so much to take in at this park. There are attractions that your whole family can experience together, such as Spaceship Earth and The Seas with Nemo & Friends. Again at Epcot, if some of the older members of your traveling party want to experience more thrilling attractions such as Test Track, there will be plenty to do for your little one, including the colorful Journey into Imagination with Figment.
One consideration to take into account in making your decision is that Epcot typically has longer hours than Disney's Animal Kingdom. Check the
Walt Disney World theme park schedule to find out hours for a specific date. If I was making this choice, I would likely choose Epcot, but that is a personal preference. I think you will have fun no matter which park you choose.
Please do let us know if you have any further questions, Shayna!