I think Sapper gave you some very good suggestions on that "other" board.
The year we did the Canada/NE cruise was on the old Westerdam (1995) and unfortunately we could not tender, because of rough seas, to the port where we were to pick up the tour for the Cabot Trail, so the ship went on to Sydney and we did the tour to Bras d'Or and the Alexander Graham Bell home. It was very interesting and the scenery was beautiful. The Fort at Louisberg is also very interesting (just saw it on TV the other day).
You have to take a whole day to actually see the Cabot Trail - DD had driven the trail with a friend the previous year and loved it, but on a ship's tour you would only be able to do part of it and as stated it could be very foggy and you'd see nothing.
Can't help with the other ports.