Hi Isabella,
Thanks for visiting the Disney Parks Moms Panel!
Mickey's Not-So-Scary Halloween Party is sooo much fun! The characters, the
"Boo-to-You" Halloween Parade, all the Trick-or-Treat’ing and more make it a great and fun event.
Isabella, you don’t mention the resort where you’ll be staying, so I don’t know where you would need to return to for your child to change into costume. Keep in mind that leaving the park and returning will take some time. Given that you will have paid a special event ticket admission, I would think you will more likely want to take full advantage of the entire event and experience all that it offers. There is simply so much fun to enjoy! Honestly, I don't think you'll want to miss even a minute of the Halloween magic.
One option to consider is for your child to come already dressed in costume. Seeing all the young guests in their fun Halloween costumes is part of the Mickey's Not-So-Scary Halloween Party experience. Even your favorite characters will be dressed in Halloween costumes!
If for some reason your child wants to meet a character while not dressed in costume, you could consider carrying the costume with you or using one of the
locker rentals.
I'm sure you'll have a very happy and not-at-all-scary fun time at Halloween.
Enjoy your Disney!
Jerry