Welcome to the RTA Forum!

Since you mention that you are bringing bikes, it seems like Moab, UT would be a natural fit for your trip. The place has a well deserved reputation as being the mountain bike capitol of the US. Its possible you are including that in your trip out to Colorado?

You also appear to have completely skipped over northern Arizona in your planning. Leaving Durango there are a lot of things that I personally would consider far more interesting than 4 corners, including Mesa Verde, Monument Valley, Walnut Canyon, Petrified Forest, and of course, the Grand Canyon - any of which could easily be included on the trip between Durango and Flagstaff.