Speaking of Rivendells, Lake Pepin and the Anderson House Hotel:
At least randonneuring has become popular enough that there is now a full brevet calendar that allows riders numerous opportunities to piece together a full series.
It really is impossible to find a Summer weekend free of schedule conflict in this part of the country. The weekend following the TdP and proposed Midwest Riv Rally is MS150, of which a few of the 4,000ish riders will undoubtedly be RBW types, who would be torn between the Rally and a supposedly good cause.
At least the TdP is one day only, going the other direction, and two of the three route options would not interact with the proposed Riv Rally at all. I'm tempted to assume that most/all of the Riv Rally people will try my secret magical back road route, thereby avoiding the Harleys, other cycling events, and almost everybody else who flocks to Pepin on summer weekends.