Oops... you mentioned broken spokes. Once one or two spokes fail on a wheel, it usually means you're at the end of the life of the wheel. Have that wheel rebuilt with high-quality butted (1.8/2.0) spokes. Butted spokes are more elastic, which build a stronger wheel*. Choose a wider rim if you're really loading the bike down. Otherwise you'll continue to break spokes, and with higher frequency on your tour.
*"The Bicycle Wheel" by Jobst Brandt is a great read for someone who may need to do wheel repair on the road in the "middle of nowhere."