Halloween costumes for children - k-6th grade..

am... creating and donating some costumes for children in need for a school.. that.. is in a poor area of town... they have a "parade" of costumes.. and don't want any child left out..

so... any ideas.. inexpensive.. is the idea... plus.. perhaps.. something that would "fit".. different sizes... like a "ghost".. a sheet.. would fit several sizes..

any and all suggestions... would be appreciated..

thanks.. freewill