Good points made; use it as a chance to hone your performance skills. The thing might grow in popularity and become more lively which will give you more folks to watch and pick up some tips from. See if you can talk to the bod on the sound desk to find out what kinds of mike are being used and the best distance to position yourself.

In terms of repertoire I agree that shorter punchy numbers with a jokey or bawdy edge or a twist in the tale are good material to use. Make sure you know the material well and focus on delivering the song through the mic. It will get easier with practice!