Guest 13 years of age and under are permitted to wear costumes that includes masks “as long as they provide unobstructed peripheral vision at all times with openings that allow the eyes to be fully seen.”
Costumes and masks are not permitted to be worn by guests ages 14 and older (except when special event costume rules apply).
Additionally, Disney has shared a few recommendations for other ways to remain in style while visiting Batuu.
Guests are welcome to wear outfits inspired by the First Order, the Resistance, smugglers, or droids’ looks as shown in the image above. With regards to the residents of Batuu, their unique style is easy to replicate by sticking with a color palette of muted earth tones with a focus on natural materials that have a rugged, handmade look.
First Order Stormtroopers will be about patrolling Black Spire Outpost and to “avoid any mix-ups, guests should not wear armor or uniforms. Also, you’ll only see one Wookiee – Chewbacca – around the village, so no wook-alikes will be permitted.”
Source: Disney Parks Blog