Homeless -- you don't mention if you're playing through a sound system or acoustically. If you don't have a sound system, I'd go for the bass - the volume and pulse of only three instruments can get quickly lost in a hall with dancers' feet shuffling and a caller barking out commands. The beat of a bass can usually be heard above a guitar or banjo. Also be aware that some callers have certain dances associated with specific tunes -- if they ask for "Soldiers Joy" or "Sailors Hornpipe" (or whatever) you either have to know the tune or be able to quickly negotiate a suitable substitute.