If some of your party could be at the YC/BC Marina on time, I believe you could talk your captain in to circling back to pick up the rest of your party (if you were only a few minutes late).
Also, part of our cruise was a tour of the waterways, including MGM. Highly unlikely, but perhaps worth a shot... picking up your group at MGM. We made arrangements to pick up some of our party at the Boardwalk by visiting the marina late afternoon and talking with our captain. Either way, visiting the marina, even a day or 2 before, could pay off.