Give me my scallop-shell of quiet

This summer, some friends and I are cycling from London to Norwich and back on a musical bicycle pilgrimage, Song Cycle. I'm looking forward to it very much and have been gradually increasing the amount of cycling I do so that I'm not completely knackered by the journeys. I've also been looking at repertoire, which is proving to be a bit more tricky. I will be limited in the number of instruments...