Any specifics about where in MA you will be visiting?
I agree with most of the recommendations for the restaurants out in Worcester but would add that you must stop at the Crown Bakery on Gold Star Blvd for some of the best Swedish pastries. I live in Boston and have them shipped to me they are that good.
If you will be out my way – Boston, North Shore to Gloucester/Rockport there are many not to be missed places – Belle Isle Seafood in Winthrop serves great seafood and huge lobster rolls. Woodman’s and The Clam Box in Essex are great. Wm Murray Seafood in Rockport is awesome – order you lobster steamed and eat it overlooking the harbor on paper plates.
If in Boston proper then Giacomo’s in the North End has great food – join the line at 5 p.m. and order off the blackboards. Mei Sum Bakery in Chinatown for Banh mi, egg custard tarts or great pho across the street at Pho Ha. Jacob Wirth around the corner on Washington Street for a beer and bratwurst. Cambridge – take the T to Davis Square to Red Bones BBQ or to Harvard Square to have a burger at Mr & Mrs Bartley’s Burger Cottage.
Hands down best restaurant for a nice dinner is Troquet, IMHO. It can be pricey but memorable.