I wouldn't be too concerned about a return route. While not an ideal destination, you can do an Orange Line return to the loop from 51st and Pulaski station and there are a lot of restaurants along Pulaski on the way to 51st Street. The Pink Line is also a station at 21st and Pulaski.
I thought this was a nice long route. While I think the food donation is very kind hearted and should be encouraged, the logistics of a tour idea were not well thought out IMO. From my standpoint, it seemed that most people who had donations wanted to drop them off then hit the road. Furthermore, from what I observed and the murmurs I heard, 90% of that crowd was not interested in a tour, and wanted to take off. The crowd seemed to be left confused and worried about a means to get back to the Northside. I hope I didn't ruin any plans, but upon seeing this and waiting for a decent period of time, I was the one that took the initiative to yell everyone to continue and charge down Pulaski to continue (quite empowering if I may say so). What are you thoughts on this?
Some pictures from the start of the Critical Mass ride last Friday: 9/27/13: