Hi Brayanne.
While a Military Discount is usually offered for
Mickey's Not-So-Scary Halloween Party, it's generally offered only for the earlier parties taking place during the month of September. By the time of your arrival mid-October, you'll want to make sure that you've picked up some regular tickets for the party for your family. You can purchase your tickets right online so that you have them ready and waiting for you at your Walt Disney World Resort hotel or Guest Services location in the parks. I've included a link for you just above.
There is no need to use both a regular park ticket and Mickey's Not-So-Scary Halloween Party ticket if you're only visiting Magic Kingdom in the evening. All that is required to enter the party is your special event ticket. If you do plan to be in Magic Kingdom during the day and night on party day, then you will need to use a park day as well as purchase a party ticket.
My family usually spends the day of a Special Event party like MNSSHP or Mickey's Very Merry Christmas Party relaxing at our Resort, strolling Downtown Disney or enjoying a Disney Water Park. We then look forward to the evening's festivities and only enter the park for the evening using the Special Event ticket.
It's up to you! ... However you choose to spend your Disney Day - it's sure to be magical!
If you have additional questions, please feel free to write me back Brayanne. I'd love to hear from you again.
Wishing you safe travels from Hawaii and a simply Magical time at Walt Disney World!
Kirsten