It would probably get quite expensive if you want to hire the band and venue for rehearsals beforehand.. If they're really good players then they'd probably be OK as long as you told them which songs you wanted to sing (and made sure you knew the keys!). That might not be much help to you, though I'm sure the emotional impact of your performance will be more important than the slickness.

Otherwise you chould try forming a scratch band with members of your family! Best of luck whatever you do