Sound setup for live ceremony music

Hello, I am considering asking my brother and cousin to play guitar and violin for the prelude and recessional music during my outdoor ceremony. They have played together before casually for family and are both good performers individually. My question is about the setup. My brother has a good amp for the guitar but my cousin only has an acoustic violin. Does anyone know if this would be loud enough for the ceremony? I am not very familiar with string performances for weddings, do they typically use amps or microphones or do they just play acoustically? Thanks