As most of you are out of town, the best option is to fly. The closest airport is Syracuse (SYR). JetBlue Airline flies out of Long Beach, CA and will connect to NYC then to Syracuse. They also fly out of Boston to Syracuse via NYC.
Once you get to Syracuse, you will need to rent a car. The drive from Syracuse to Wellesley Island is about 1.5 to 2 hours. Follow the direction in the "By Car" Section.

