If you end up using a hard case like a Pelican, just hope you don't have any portages. I'm getting this picture of you carrying a canoe over your head (which takes two hands) and somehow trying to hold a Pelican case. You'll need a third arm.
If you had a good padded backpack-style camera case you could roll up the dry bag when portaging and more easily carry your gear. (Regular backpack on back, camera backpack on front.)
Or, suppose you stop and camp for awhile and want to hike around with your camera. Again, you could ditch the dry bag and just use a normal padded camera backpack. Can't see you dragging a Pelican case through the woods on a hike. Only advantage of a Pelican that I can think of is that it would hurt a charging moose more if you threw it.
In my opinion, you have to decide whether you are going on a photo trip that just happens to use a canoe or a real canoe trip where you want to take pictures, but will still have to run rapids, do portages, take hikes, etc.
My two cents from an ex-Minnesotan.