If you are going to do other non-supported tours then you need a bike constucted to carry panniers or at least pull a trailer. If you are going to ride other supported rides, like CNC, then any good road bike will do. All of the major manufacturers make bikes for centuries, unloaded touring, and the like. Just be sure it fits properly and that you have fine tuned the seat, seat height, stem length, etc. before the ride. You will probably want a triple or compact double, unless you are young, and/or a glutton for punishment. I have ridden 30/42/52 with 13-28 cassette twice, and this year will ride a compact double with 34/50 and 13-29. You only lose one gear over the triple. All frame materials are equal in my mind, just be sure the salesperson knows you are going to be on the bike for 4-6 hours a day, seven days. It is a long time to be uncomfortable. Any frame material can make a stiff, strong frame and any material can make a wimpy, whippy, likely to break frame. You have to ride the bike and read the reviews at roadbikereview. Personally, I would look for a drive train that includes Shimano 105 or above or Campy Veloce or above. I do not know anything about SRAM but I love their mtb stuff, so I assume the road gear is high quality.
You could also look into the recumbent bikes that are out there.There are numerous dealers around now and they are so much more comfortable than a road bike(wedgie). I like RANS,Go to www.ramsbikes.com
Thank you for all your expertise! At least now I may begin to shop with an idea of what to look for in a bike. This is a whole new experience for me, and I am looking forward to it.