HI Michelle! This is one of my favorite shows to augment cast! A big ensemble in this show makes the music (that is already top shelf), even more fun! The simplest solution is to have GUYS galore, and yes of course these can be girls! They love the "gangster personna", and suit up easily! MISSION BAND can include members of all ages, even if you add more of them simply in scene 13, or each time the MISSION comes through the house in an entrance/exit. NYC pedestrian types,(bums, gamblers,gals) can be added to set the scene during the overture,scene 13 and scene 15, the wedding. The Havana scene is a fabulous opportunity to add "club musician types", dancers, waiters and restaurant patrons. I hate to be trite, but the more the merrier in G & D, as long as you tell the story clearly!