Adventure Cycling and Sheldon Brown both offer sound advice on touring builds. Usually the advice consists of "simpler is better". The suggestions here are also good, but I didn't see anyone stress that a weekend rider like myself may greatly appreciate the MTB gearing for climbing. Even without a significant load, there's a sense of accomplishment to climbing without having to push!

I hope to live vicariously through your tours! Family commitments mean I can't use a week of leave to see just how far I can go!