Cobbs Mill Inn - Weston, CT
I can tell you that for "Olde New England" ambience, Cobb's Mill is the ticket. It is not, however, a Chowhound destination. The restaurant food quality fluctuates wildly; there have been multiple chefs in the last 18 months, and the place has been on the market for a while. However, to your advantage, the banquet chef has been the same guy for years and years. He knows how to execute an event efficiently and with consistency, as does the waitstaff, some of whom have also been there for years. My boss's daughter had her rehearsal dinner there, and all were happy with the affair.
If you are looking for a prime rib/grilled salmon type deal, they will do it right. If you are looking to have anything more creative, you might want to investigate other options (Bernard's in Ridgefield comes to mind - really top notch). For comparison to other "country" inns in Fairfield County, I would say Cobb's Mill is better than Silvermine Tavern in Norwalk (truly ghastly event food) and comparable to The Spinning Wheel in Redding.
Good luck & congratulations!
ps. It can get mighty cold in some of the downstairs dining rooms - be forewarned if you are planning a winter/spring/fall event.
Disclaimer - my boyfriend did a brief stint in the kitchen at the Cobb's Mill, which is how I have information on the workings behind the scenes there. This in no way influences my opinions on the place, which come from personal experiences and those of friends/family.