David, I’m sorry to answer so late.  
I just saw this.
Ride leaders choose start location, route, and time.
The RL may post or ask me to post their chosen route.
I try to remember to post the ride on Facebook.
At the start of the route, have a show of hands for each route if more than 1 route.  Any unusual turns or hazards that one is aware of should be noted.
There is no requirement for a sweep although some do provide that.
I do note when I return those who haven’t and text later to check if needed.  There are mostly none for me since I ride a slower pace.
If only two people show up,  which is rare, they should ride the slower persons pace.