I think that's the same rafting site Richard (my husband) found:
http://www.tidalboreraftingtours.com/
that's where we got the dates I put in my first post. He wants to plan the trip around one of their "peak tide" dates if we can.
Sure, it'd be simpler to fly into Halifax, but that's $760 more for the plane tickets than flying into Bangor. Even though car rental rates in Halifax are a bit cheaper -- we'd save about $50 total by renting in Halifax vice Bangor -- and we'd have to budget for an extra night's stay getting from Bangor to & from the more interesting areas, it doesn't balance the initial wallop.
I'm also keeping track of individuals renting rooms via Craigslist; we got our room in Montreal that way & it worked out very well, cheaper, more fun & more interesting than staying in a hotel.