Falmouth area has better fishing than diving from what I remember. Lots of blues and stripers but you may want to find some fish reports before you go. Not sure of the regulations either it has been a while. But a RI license may work in MA...
May look into some shore dives like Fort Wetherill RI or Cape Ann (Gloucester) MA - not sure if it is worth trailering the boat to either place since shore diving is fairly easy.