Hi Jann,
I love the way you think! My very favorite time of year to visit Walt Disney World is around Halloween, followed closely by Christmas, so getting to experience both in one trip would be a dream come true!
With the right planning, I do think you will be able to enjoy a bit of both holidays during your visit. Typically, the transformation of the decorations in the parks and resorts from the pumpkins and foliage of fall to the trees and sparkling lights of the Christmas season usually begins after the last day of
Mickey's Not-So-Scary Halloween Party and is complete by the first day of
Mickey's Very Merry Christmas Party. This year, those dates fell on November 1st and November 8th. While Cast Members are hard at work behind the scenes that whole week getting the parks and resorts decked out in their holiday best, much of the work is actually done overnight. One of my favorite videos from the Disney Parks Blog -
Time-Lapse Video: Magic Kingdom Park Decorated for the Holidays - gives a fun peek behind the scenes to show how this is done.
As you finalize your plans, I'd recommend keeping an eye on the
Disney Parks Blog for the 2016 dates for Mickey's Not-So-Scary Halloween Party and Mickey's Very Merry Christmas Party. This year, those were announced in late February, so you may not have to wait long.
Wishing you pixie-dusted planning for your vacation, Jann! Please write back if we can help answer any other questions.
Beth