Greetings Alex,
Congratulations on planning your next Walt Disney World Resort vacation. No matter how far away it may seem now, it will be here before you know it.
Although, Florida weather is hard to predict, September is my favorite time to visit the parks because usually the weather is nicer than the summer months and the crowds are a bit lighter. It should be similar to April, perhaps a little warmer and can have a greater chance for thunderstorms, but they are usually short in duration. Truly, the decorations and events throughout the
fall at Walt Disney World Resort trump any atmospheric nuisances. The parks are so beautiful! Two of my favorite Special Events also take place in September:
Epcot's International Food and Wine Festival and
Mickey's Not-So-Scary Halloween Party. Your son (and the rest of the family) will definitely love the later event. A special parade and fireworks, your favorite characters dressed in fun costumes and even trick-or-treating in Magic Kingdom Park make for a magical night filled with memories.
Have a wonderful time planning your autumn adventure and if there is anything else I am able to assist you with, please don't hesitate in sending another question my way.
Magical Wishes,
Lauren