I've day dreamed of riding a small bike on an adventure such as you've undertaken, but for me a small bike would be something like a 250cc! Man, you're a true minimalist! I've enjoyed reading of your progress and wish you continued good luck.
I would most definitely recommend going to Death Valley. It's a special, beautiful part of a beautiful state. The Grand Canyon? NO WAY! It's too late in the year for that. Though the canyon is deep, you must not overlook the fact that the rim is still very high. One of my coldest rides ever was passing through Flagstaff (near the south rim of the Canyon) in late summer. With what appears to be extremes of weather becoming the norm, I'd not venture into higher elevations this late in the year - no matter what bike I was riding.