regional seafood, not gourmet!
If you're willing to get out of boston and into Cambridge, go to Summer Shack. Its Jasper White's seafood restaurant where you can get anything from a corndog to wood grilled lobster.
We also just ate at the Barking Crab, down in the harbor and enjoyed our food. It has that clamshack appeal as well, and is on the water with outside seating, or at least a tent with open sides.
Enjoy your visit.