I like SongBob's suggestion too, as "ballads" is a really huge category.   
One way to deal with lists might be to have a whiteboard or sheet of newsprint at the side of the room where someone could write the name of each song after it's done (if someone was willing to play scribe). That way a newcomer wouldn't have to start into "The Four Marys" only to be told that it's already been done.


Oh, and, Bill D. ("I can play reveille on a soprano recorder - but I know better than to do it.)
I can play the entire "Stars & Stripes Forever" on a kazoo too. But I also know better ...