[littlemanbighorn]

Provide a list of all the songs you can do. (Just like a Karaoke machine). Be prepared to transpose it for the singers range (though much of the fun for Karaoke is trying to crack it out like the original... and failing miserably at it).

I wouldn't worry too much about getting the range right. It's up to the singer to pick a song they can do, they'll only learn what's in their range if they get stuck with some things outside of their range.
Plus: It's not like they'll be in tune anyway. I've got tonedeaf neighbours downstairs with a karaoke machine. Awful.