New Haven (City) has so many good restaurants! For a group of that size, I'd recommend Kitchen Zinc. They have innovative and awesome food; I'm 99% sure they have a private room. We took my parents there and they loved it. L'Orcio is Italian and has a private room that accommodates up to 45 people (according to their website) but I've never actually been there. Caseus is a personal favorite but you'd have a hard time getting that many people in there- I don't think they have a private room available.