I've done it twice-- the first time in 3 days, with overnights in Hancock & Harpers Ferry. More relaxed, there were ten o fus. It was very enjoyable. The second time was with one buddy-- we decided to try and do it in one day. Drove to Cumberland, left the car there. Early in the morning we started (on mountain bikes). 13 1/2 hours later we were in Georgetown-- averaged about 15 miles an hour. We got rattled. My arms were sore from the jarring. I had no suspension on my bike. Tony had suspension and was a little better off than I was. At any rate, it was a great ride-- we had good weather, which helps, and dry conditions throughout.
On your list, why a pump and CO2 cartridges. Leave the CO2 at home. The pump is all you need. I would also add a light jacket-- goretex if you have it, as it could rain on you, or it could get cold. (I know, August it is unlikely--but it is better to be prepared... or if you don't want to take a jacket, bring arm warmers).
Regardless, it should be alot of fun-
enjoy-
train safe-