Hi Ariana,
Thank you so much for visiting planDisney with your question!
Mickey's Not-So-Scary Halloween Party is a delightful event.
Magic Kingdom comes alive with lights, decorations, parades, and characters in costume. You can attend in costume, and it is really fun to dress up as your favorite Disney character! It is even more fun if you can get everyone in your party to dress up for a specific theme. One year, my family all dressed up like fairies, including a fabulous Tinker Bell!
Mickey's Not-So-Scary Halloween Party is a separately ticketed event, meaning that it is not included with the price of a daily ticket to Walt Disney World theme parks. I love that you plan to go to
EPCOT earlier that day, and that you already have a theme park reservation! What you need to do is to head to the website I linked from Mickey's Not-So-Scary Halloween Party and purchase tickets for that event for yourself and your traveling party. Once you have those tickets, you will be good to go!
On the day of the party, you can head directly from EPCOT to Magic Kingdom using the
monorail when you are ready if you want to head directly from theme park to theme park. You do not need to make a theme park reservation for Magic Kingdom on this day as your Mickey's Not-So-Scary Halloween Party Ticket will act as your reservation for this event. And bonus: you can head over to Magic Kingdom as early as 4:00 p.m. with this event ticket if you like!
I hope that this information is helpful for you, Ariana. Have a wonderful time planning your magical trip, and please do let us know if you have any further questions!
~ Mona Leigh