"Run, Freedom, Run" from URINETOWN is an excellent group number for a finale. The vocal selections book has the voice parts for the 'choir' in there. You could also use "You Can't Stop the Beat" from HAIRSPRAY. There is two part harmony written in the vocal selections book--but the other harmony parts are doubled in the accompaniment--so if you have someone musically bright you can easily make it 4-part.
"You pile up enough tomorrows, and you'll find you are left with nothing but a lot of empty yesterdays. I don't know about you, but I'd like to make today worth remembering." --Harold Hill from The Music Man
