I made it across the country on a Randonee, so it'll work for touring. Make sure the mechanics know what you're planning for it and work the wheels over; by default they're the standar machine built wheels, and will likely start breaking spokes. (That's true for any production bike, IME.)
I have a Fuji Touring from way back when; my perception is that it's a little bit lighter and sportier/twitchier than the Randonee. I prefer the Fuji for light / fast riding, but the Randonee for riding with a load. The Trek 520 I test rode seemed to me to be more like the Fuji, and the LHT was on heavy side of the Randonee. Try them yourself if at all possible, YMMV.
You might have to extend your search radius; I ended up calling all the Trek and Cannondale dealers within about 4 hours' drive to find the second nearest REI had a Cannondale Touring bike (back in 2006, IIRC). When I got there I decided I liked the Randonee better. Go figure!