Hi, Cailin!
This is a great question! My family will actually be visiting Walt Disney World Resort during the same time that you've planned your trip. On past visits, we've experienced both Mickey's Not-So-Scary Halloween Party and Mickey's Very Merry Christmas Party. While I've enjoyed both parties, my definite preference is the Halloween Party. My 7-year-old daughter first experienced the Halloween Party when she was just shy of 5 years old -- she LOVES the Halloween Party and wants to do it again every year! The special Halloween parade and fireworks are, in my opinion, the best that Walt Disney World Resort offers. There are also dance parties with characters from Toy Story and Monsters, Inc. and an amazing Disney Villains show performed on the stage right in front of Cinderella Castle.
Mickey's Not-So-Scary Halloween Party will more than make up for your girls having to miss trick-or-treating back at home due to travel. We are in the same position and my daughter is really looking forward to doing the treat trails and meeting some of her favorite characters at the Halloween Party, especially the rarer ones like all Seven Dwarves and Flynn Rider with Rapunzel.
I would recommend
purchasing tickets for Mickey's Not-So-Scary Halloween Party online as soon as possible. I suggest choosing the last party date, November 1st, since the October 31st party is VERY popular and tends to sell out in advance every year.
Jennifer Fickley-Baker recently posted an
article on the Disney Parks Blog with tips for first-time Halloween Party-goers. Just click on the link for all the details!
Wishing you a spooktacular good time!