I was going to suggest you do a websearch for Joe Kurmaskie, so it's good that you've already had a chance to talk to him in person. From past stories on bikeportland written about him, I know that he's set up and used a multi-rider combination bike, tagalong, and bike trailer that would do just about exactly what you need.
There's even a picture of it somewhere in the bikeportland archives. Just looking at the pic, it seemed like an awkwardly long, heavy thing to pedal and keep track of, but if I remember correctly, Kurmaskie rode the thing loaded around the country. Amazing things can be done.