Hi Colleen, welcome to the Disney Parks Mom's Panel.
Mickey's Not-So-Scary Halloween Party is an awesome family experience to enjoy while at Walt Disney World.
This event starts at 7:00 pm and guests with the special admission ticket are allowed to enter the park since 4:00 pm.
On most nights, during the late hours - after 10:00 pm, the park crowd levels drop significantly allowing guests to enjoy the park in a unique and special way - it is really nice to enjoy the attractions with little to no wait.
To make the most of this event I suggest taking a good midday nap and early dinner before heading to the park. Also, for the day after it is better to stay at your resort and enjoy the pool and other recreational activities.
This way you will not over schedule your vacation and you will be well rested for the rest of your vacation or for your trip back home.
Thank you for visiting and letting us help you plan a Not-So-Scary Disney vacation.
Hope to hear again from you.
Miguel