Hi Haley,
I love the Walt Disney World both times of the year! April is great for a spring trip, and as long as you are not traveling around Easter or Passover, you will see low crowds, cool weather before the humidity arrives and even a special on a package.
Epcot International Flower & Garden Festival is also beautiful and there are great tips to get your outdoor areas ready for the summer.
Personally, I would go in October as it is my favorite month to visit. I love the weather and the lines are shorter because the crowds are lighter. There are two fun events I love.
Epcot International Food & Wine Festival Presented by Chase is a fun event around World Showcase. Each country plus many additional countries have kiosks with food and drinks from their country. It is fun to try new foods. Magic Kingdom has
Mickey's Not-So-Scary Halloween Party. This is one of the few extras I would pay for on my vacation. You can dress in a costume and trick-or-treat around the Magic Kingdom.
You also will find deals in the fall as well.
Wishing you a magical vacation!
Beth