Outdoor Wedding Ceremony?

I would recommend Mt. Holyoke because a friend of mine had her wedding photos done there when I was in her wedding years ago and it was beautiful, but like you said, if it rains you have no backup location. So a country club would be optimal if they have nice grounds. Another idea is to look at vineyards in the area, they usually have beautiful gardens. You could have your ceremony up to an hour from where the reception is, that's a reasonable distance to ask your guests to drive, don't worry.