Hi Darrel,
Welcome to the Disney Parks Moms Panel and thank you for asking us a question!
Although Guests 14 years and older usually can’t wear costumes when visiting a Walt Disney World Resort Theme Park, the rules are relaxed at Magic Kingdom Park on nights when
Mickey’s Not-So-Scary Halloween Party weaves its spooky spell in the Park. Guests of all ages can wear their favourite costumes, so long as you follow several guidelines, including a prohibition on items that resemble weapons or that could be mistaken for a weapon of any kind. Please follow the link I’ve included above and go to the "Costume Guidelines" section for more information about what types of costumes are allowed for your upcoming visit.
From what I understand, while Guests 13 years old and under can wear masks, provided their masks don’t cover their entire face and their eyes remain visible. Please note, however that masks are completely prohibited for Guests 14 years of age and over.
Please don’t hesitate to come back and see us if you have any other questions.
Have a Magical Day,
Lynne