My fiance and I are staying within the US for our honeymoon the second week of September, but can't decide where to go! Our top three choices are Vail/ Boulder, CO, Napa Valley/ San Fran, and Mackinac Island/ Traverse City, MI. Does anyone have any input on those destinations? It will be September so Vail won't be as expensive as it usually is, but at the same time I'm wondering if there will be enough to do and see there during the summer? I've been to MI many times before and love those little resort towns on Lake Michigan, but the FI isn't really convinced. Any feedback from previous experiences would be appreciated!