Our group is doing it early summer also, and many have already done it. I've done parts, but not the whole thing.
There are a couple of resources worth checking out.
THe C & O Companion (Mike High, I think)
Shay and Weil (check out their website.....you can find them using a keyword search of their names or by using the title "Freewheeling Easy") "Freewheeling Easy" is their resource about trails, etc. in the Western Pennsylvania area, although they also have a specific compendium dedicated to the C & O...It is only a couple of bucks and you can buy it on their website. They provide many good tips, including places to stay, eat, camp, etc.
They recommend starting at D.C.....claim it's a more scenic ride.
Regarding the touring bike/tire issue, others may have more reliable recommendations. The parts that I've ridden, I'd say you would be fine, but I haven't done the C & O in its entirity.
I'm happy to provide more information as I come across it since we're doing it in early June.