Kids dressed as SHADOWS for Halloween - their mother bought black morph suits for them then layered black clothes over those. This may be the scariest thing ever! ^^^ I was a shadow last year, but I just wore all black clothes and a cape.
DIY Peter Pan's Escaped Shadow Costume (or Just a Regular Peter Pan Costume). Would be cute for a duo, one dressed as Peter, one as the Shadow. Or family dad as Peter pan, son as shadow, mom as wendy and add characters as need be
Of course could do the Twisted version as Bobby Driscoll's shadow. Clever Halloween costumes (Peter Pan's shadow) l Could be adorable some day for the girls. The whole family could be Peter Pan characters.