Mark - My advice is very basic. I have canoed and rafted on two long trips and never take my Canon G5 (been too chicken) but I wished I had taken my old Canon (2 mp). My trips have been on big lakes, rivers and whitewater in Maine and whitewater in Idaho. Weather is as much a threat as falls into the river.
Sounds like you are packing your own gear, (not outfitter/guided) correct? The Pelican case sounds good. Hopefully it allows quick access to your camera but I always find canoeing keeps me so busy that taking pictures is a far second activity when on the water, especially if kids are around. Use a large carabiner to attach your small dry bag or Pelican case handle to the canoe thwart. Bring a few extra carabiners to attach things as needed.
Don't laugh, but our Scouts have had excellent luck with getting a wide variety of on the water pictures of everyone in the group using waterproof cameras with the long rubber bands that can be hooked right to their PFDs. We develop them on cds and edit using Photoshop Elements.
As to getting memorable camping pictures go for the everyday activities such as putting up tents, loading the canoes, cooking meals, washing dishes, dirty faces, and sleepy heads waking up in the morning. Take a picture of each site to keep track of your trip later. Be sure to take a group picture at the beginning AND at the end to show the wear and tear! If you can have real campfires be sure to try for a picture. I love campfire pictures with people in the background. Get the nitty gritty and the beauty of paddling. I always wanted to catch the paddle mid-stroke dripping...........canoes in a rows and so on
Have a wonderful trip and let us see the results!
Here's a few of my fave's taken using an older Canon: