See if you can find the forum member (nancy sv) and her family's touring adventure thread on this forum as they traveled from Alaska to the tip of South America. I remember her stating that they would only use 26" tires in the future because finding 700c tires and wheels down there was really tough. Plus she would be an excellent resource for information on epic journeys (especially if you plan on hauling your two children with you). Best of luck.

Family on Bikes