I think 23's will be a little too narrow for comfort on the C&O, but you could probably do it. When I did it it I ran 35's, which worked well. If you can get wider tires on the Panasonic (28's, maybe?) that would probably work.

It rained one of the days of my ride, and there was mud, but it was never deep enough that I was worried about sinking into it. It just made a mess of all our bikes.

Chris