Kent,
The Shearwaters are good boats and will do just fine for what you described, but you may also want to consider the Wood Duck 12. I'm basing that on your description of the river. The WD12 is shorter and lighter, which makes it easier to turn and maneuver in restricted spaces. The lighter weight makes it easier to accelerate (though it's not as ultimately fast as the Shearwater). It's also less akward to carry. Another reason for the WD12 is that it is more stable than the Shearwater.
How does this work in with your river? I hang out a lot on similar-sized rivers and here's a typical trip in my WD12:
Unload from the rack on my truck and carry it past all the fishermen illegally using the boat pier to fish from. Under 40 lbs and 12 feet makes it easier to clear all the poles and junk they have scatteried on the pier. Even better, when the tide's right (this is a tidal river) I can launch from a sand beach.
Put on an extra burst of speed to get throught the eddy at the end of the pier. If caught, turn while accelerating to get into the main channel. Once away from the pier, paddle more slowly. Go upstream in a small tributary, threading my way between water plants, submerged tree trunks and under canopies. Get to the old beaver dam where a break is channeling water from upststream. Put on a quick burst of speed to shoot the opening while turning left. 12 feet lets me get the entire boat through, instead of jamming in the hole. I've now given the slip to all power boats, jetskis, sea kayaks and canoes, without having to portage across the dam.
Get to the new dam, the one without any breaks. Using my paddle as a support, stand up in the boat and look out over the beaver pond. See the deer, beaver, muskrats, birds, turtles, etc. that would be invisible from the bottom of the boat.
Head over to my favorite frog pond and listen to the bullfrog serenade during lunch. Slide down into the boat and take a nap, using the seat and my PFD as a pillow.
The WD12's size and weight make it more convenient for a small river. The Shearwater's sea kayak-like characteristics make it more suitable for a large river or estuary. Either will work very nicely for your situation, but since you asked for advice, that's mine. Consider the WD12.
Whichever you choose, you're going to have a nice boat for your new home.
Have fun,
Laszlo