Please help me with my talent show act?

Okay, So I'm planning to do a medley with a girl and a guy. The girl is going to be singing with me. The guy i going to play guitar. The guy is unsure if he wants to do this at the moment. So if he can't, we have to do it with the instrumental version of songs. Then there's this other girl who would like to join us. Should I add her to out act? More people the better? By the way, I'm a girl too.