Hi Nataly,
Thank you so much for visiting the Disney Parks Moms Panel with your question.
Mickey's Not-So-Scary Halloween Party is a truly unique experience! My daughter love dressing up for this event - last year she went as Lilo. Trick-or-treating around the Magic Kingdom is so much fun, and be sure to see Mickey's Boo-to-You Halloween Parade and Happy HalloWishes fireworks - they are amazing!
You ask an excellent question. The answer is that to attend Mickey's Not-So-Scary Halloween Party, you only need to purchase the ticket for Mickey's Not-So-Scary Halloween Party. You do not need separate admission to Magic Kingdom that evening. Typically in the past, guests with tickets to Mickey's Not-So-Scary Halloween Party have been allowed to enter the
Magic Kingdom starting at 4:00 p.m. even though the party itself starts at 7:00 p.m.
I hope that these thoughts are helpful for you, Nataly! Have a wonderful time planning your magical vacation, and please do let us know if you have any further questions.