Well the intention in Baltimore was never to "ace" the system --- Been there done that. If need be we can arrange to turn back sooner than BWI Airport on the light rail, or well before the Owings Mills terminus on the heavy rail.
A concern I have is that everyone (potentially 18 of us as of now) has to purchase a Day Pass after we get to Baltimore, and as it stood before the recent MARC announcement, we only had about 12 minutes to do so. The Penn-Camden shuttle light rail line runs on 30-minute headways, so if we end up missing the intended trip we have to wait another 1/2 hour until the next one. That might result in us just going south on the light rail only to Lexington Market for lunch, and doing all or part of the Metro heavy rail. We'd probably have to cut out the BWI Airport segment.
One way to save some time in buying the Day Passes would be for fewer people to make multiple purchases is that is possible --- in other words one person buying 18 day passes with one credit card, and then that person is paid back in cash later on. I don't know if multiple day passes can be purchased, or if so if there is a maximum.
Washington Metro concerns me too, if they pull that 24-minute headway stunt. It could be a long wait if our chosen trips are not the ones still running.