Hi Julie and welcome to planDisney.
My family are currently at
Walt Disney World and are very excited to be attending one of the Mickey's Not-So-Scary Halloween Parties, next week. If you haven't attended one before, let me tell you that they are a lot of fun! There's Mickey's Boo-To-You Halloween Parade, Disney's Not-So-Scary Spectacular, dance parties, character meet-and-greets with Disney characters in their Halloween finest and much more to enjoy. Not to mention the fact that you can trick-or-treat throughout the park and make the most of lower wait times for attractions than you would find on a typical day.
Going back to your question, although the cost of 1-day park tickets to the
Magic Kingdom do vary depending on the date of your visit, tickets are not any cheaper on days when
Mickey's Not-So-Scary Halloween Party will be taking place.
For this reason, if you will only be spending 1-day at the Magic Kingdom during your trip, in order to to get the most out of your visit, I would recommend visiting on a day when the halloween party is not taking place. That way, you'll be able to spend the entire day at the park, see the recently debuted
Disney Starlight: Dream the Night Away nighttime parade (which looks absolutely amazing, by the way) and stay for the Happily Ever After fireworks extravaganza.
I hope that this information has been of use, Julie. If we can be of any other help with the planning of your trip, please feel free to re-visit us, here at planDisney.
Wishing you a magical holiday filled with memories which will last a lifetime!
Emma