Hiya Sharon!
Thank you so much for stopping by! Halloween is one of my favorite times of year, and Walt Disney World is my favorite place to be, so when you put them together?!? INSTANT BLISS!! Disney Springs (formerly Downtown Disney) sadly hasn't held a trick-or-treat event in a few years.
The Campsites at Disney's Fort Wilderness Resortdoes allow guests to trick-or-treat around the campsites on Halloween. It really is tons of fun, and while not all the campers participate (they'll have signs out if they do), it's a blast for the kids to see so many of the sites decorated!
You'd need to take Disney Transportation to get to and from the Campsites, so do keep that in mind, and it is quite dark in that area, so flashlights, night visibility gear, and parent supervision is a must for safety, but I think it might be super fun for your kiddos!
Have a magical vacation!
Amanda