take a set of bike shorts, medium weight full length tights with pad and a set of wet weather gear. a light fleece top too. the olympic peninsula can get some nasty, miserable, wet weather any time of year. take advantage of the offer to have the organizer carry your extra gear if you are very certain you won't need it.
on a lighter note, this post reminds of the Seinfeld episode where Elaine has the unenviable task of buying socks for her boss.