From http://laws-lois.justice.gc.ca/eng/acts/E-1.6/page-2.html#h-6 section 9(a) reads "the person who sends the message, the person who causes it to be sent or the person who permits it to be sent has an existing business relationship or an existing non-business relationship with the person to whom it is sent;"
Thus it does not actually matter whether it's a business or non-business relationship, rather whether it's an existing relationship or not.
The details of the type of association etc might be relevant, but in general there would be a relationship between the parties as they are both members of the same association. (The act does not appear to define the meaning of the word relationship, but THE LAW DICTIONARY defines a relationship as "A particular type of connection existing between people related to or having dealings with each other." - which would seem to fit the criteria described.
Also, there is a FAQ on the Canadian legislation website which confirms you can rely on complied consent - See "What is implied consent" - "The person is a member of your organization or has provided volunteer work, a donation or a gift"