User blog comment:Tinknme96/Kid's costumes/@comment-26143371-20161025190402

The closest you can get is the Nightmare Pile. It allows you to send a youngster to Wear A Costume. However that's only a 4h job and not a full costume; and you can only send one character at a time.

This year the Nightmare Pile is only available through the Mystery Jack O' Lantern, which means it could be very expensive if you're unlucky and get all the other prizes first.