I'm not sure how far north you would like to go...but in Rye, NH (just over the border) is the Wentworth By the Sea. It's beautiful, and I've been to several different functions there. Super fancy, to garden party, to a 80's inspired fundraiser. Also, there is the Red Barn at the Links...it's adorable and cozy...and I recently went to a wedding at the Larz Anderson Auto Museum in Brookline, Ma. It was Very different than anything I've ever been to....but classy, entertaining, relaxing and a really good time!
There are so many great places to choose from, good luck finding something that suits you!