Four years ago I rode a bike from Chester Nova Scotia to Ciudad Victoria in Tamaulipas, Mexico. It took me three months, and despite being lonely, homesick, and sore much of the time it was the best thing I have done. I'm sure that you and Sho will feel the same.
Next fall I plan to walk the Camino de Santiago del Campostelo. Not as much an adventure, but challenging for a septugenarian.
For a couple of years now I've been dreaming of riding from Kagoshima to Hokkaido. I'd like to try the reverse of your trip and try to follow the Sakura (cherry blossoms) as they bloom.
Reading about your trek is an inspiration to me, and I'm thrilled about the fact that you brought your son. If I had a son or daughter (and one that was ready and willing at that) I'd be sure to take them along!