Hi Gemma,
Welcome to the Moms Panel! We're glad you're hEAR!
Mickey's Not-So-Scary Halloween Party (MNSSHP) is my favorite special event at the Magic Kingdom (MK). It does require a separate special event ticket to attend & is not included in the Disney Ultimate Park ticket. Only those Guests with the special event tickets are allowed to enter or remain in the park once MNSSHP begins. Guests who want to spend the day at the MK & attend MNSSHP on the same day will need 2 different tickets - a regular ticket for admission during the day (MK closes at 7:00 p.m. on MNSSHP dates) & a special event ticket to MNSSHP for that evening.
MNSSHP begins at 7:00 p.m. & lasts until midnight. Once party goers enter the park, they are given a special wrist band which indicates they have tickets to this event. Cast Members will be stationed at the entrances to the different themed lands. Guests who aren't wearing wrist bands for the event that evening will be asked to make their way down Main Street to exit the park.
If you decide that you are going to do both, I'd concentrate on the rides and attractions during the day and focus on the special events that only occur during MNSSHP. It really is awesome fun!
Please let us know if you have any other questions during your planning. It is our pleasure to assist you!
Wishing you minnie magical memories :-) Allison