When it comes to Bards there's really only one question: Lute or Bagpipes?

On a more serious note, if you have to go for one of those...a wealthy, formally trained Bard - perhaps a noble second or third child who got enrolled into a wizard school but preferred to spend his/her time at the tavern playing ballads until he finally got expelled from the local Hogwarts...could make for an interesting addition to the party.