Yes, the expense of a one time event is an obstacle and the trailer solutions, if purchased new, would be $150+ all they way up to an amount that is not worth spending for the Hase Trets model.
It looks as if I would be able to get the extra, low end tandem for our visiting friends rented at around a $30 per day charge with the travel to and from days being gratis.
My wife, although she would rather ride solo with her friend this year, is warming to the idea of being a captain for her daughter again on this year's RAGBRAI.
Thanks for everyone's advice and thoughts.
BB