I think unplugged session would be good enough. My music friends will play unplugged for me. One acoustic guitar and one piano is good enough for a singer. And i do have full band music friends. But i really dont intend to activate them all. Hahas... the violins, double bass, drums, percussions, rythm guitar, saxophone, pipa, er-hu, electric guitars, harmonica & etc etc. If i really activate them all, i think my wedding is gonna be a concert! Cannot larrr... I pick two of them in the band to be my emcee tho.
If full band, some people might feel a little "too much" for a wedding. Unless your guests are all those people who really appreciates musics ba. And it is quite costly to engage full band.