Harvard Square and Coolidge Corner are far from each other, but the #66 bus runs along Harvard Ave and picks up in front of the Bank of America on the corner of Harvard St. and Beacon St. and it runs right into the heart of Harvard Sqaure. If you’r going by car, just drive on Harvard St. through Allston/Brighton until you get to Cambridge Street and take a right at the light. Take the left at the second light (I think) on to North Harvard St. which becomes JFK St. once you cross the Charles River into Cambridge.
I love Shaw’s. I have an aunt in New Harbor and used to go there a lot. Hey, Red’s Eats in Wiscasset (reviewed here) is on the way to New Harbor. I don’t know if they’re open all year, but I’ve heard good things about them. If you get a chance to go to the Pemaquid lighthouse, its really beautiful out there on the point. Have a great trip!