It's fairly easy to plan a fun city group ride without it being a CM ride.

Tell your friends. Get your coop on board, post on CL with plenty of anticipation. See if you can get a local shop or two on board

Consider a full moon ride and encourage everyone to light up their bikes as much as possible. Or a canned food ride. Print out cue sheets that include stops at local groceries and the MD food bank's list of most needed food items. (just make sure to tell people to bring a bag)