Looking into the history, it seems that blackface minstrelsy was grafted onto guising, or mummery, in mid-19th c. or later, to create a regional variation. The word darky (darkey, darkie) (OED) may mean a type of lantern, night, or a Negro or blacky- the last not found in print until mid-19th c. As milk monitor notes, its use is dying out.
Expunging the minstrel addition should not destroy guising or charitable efforts associated with it.