Hi John!
Thank you for bringing your question to the Disney Parks Moms Panel. I have a similar trip planned and I'm excited to be able to catch both Halloween and Christmas decor!
Historically it happens overnight after the last
Mickey's Not-So-Scary Halloween Party, Guests will return to their Walt Disney World Resort hotels and return the next morning to Christmas decor! This
Disney Parks Blog article actually shows a time lapse of how it happens. Since the last Mickey's Not-So-Scary Halloween Party is on November 1st this year, you likely won't see changes at the Magic Kingdom until November 2nd, but I'd expect you'll see some touches in other locations. The full Christmas decor, including trees in some lobby's and around all of the parks, won't be fully completed until the second week or so into November, but you'll definitely be able to catch some of magical decor during your stay!
I'm glad you'll catch some
Boo to You! Halloween fun and some
Very Merry Christmas fun during your trip! Please let us know if you have any other questions.
-Lindsey ºOº