its always a good idea to consider the size of the venue to determine how loud you play. for a venue this small, and being a horn player with a fairly "soft" instrumentation (acoustic bass, piano, brushes on drums), i wouldnt necessarily play through a mic. but then again, if you use a mic, you dont really have to play as loud either.
i played with a group that plays in a venue about the same size as this. when i first joined them, i was a pretty loud player, and they told me to "tone it down a bit. everyone can hear you just fine." and i was playing without a mic. nice playing, but maybe a little too loud? thats just me though.
