I'm 60, and I'm planning to ride the entire GAP-C&O Canal trail from Pittsburgh to Washington DC in June with some friends. We are going to stay at inns and hotels along the way rather than camp out. Our plan is to drive first to DC, park our cars, and take the Amtrak to DC with our bikes. When we get to Pittsburgh, we'll stay at a hotel near the train station and head out the next morning, riding about 60 miles a day until we get back to DC.

You can find everything you need to know about the GAP and C&O trails at this website: http://www.bikecando.com/

BTW, there are various businesses that offer shuttle services along both trails. So you can park your car, ride as far as you want on your bike, and take a shuttle back to the finish -- assuming you have pre-arranged the details. Amtrak is really only an option if you are riding the entire trail from DC to Pittsburgh or vice versa.