Of course car is easiest and the hotel is located right off exit 60 of the Long Island Expressway. There are viable public transportation options too such as taking the Long Island Rail Road to the Ronkonkoma station which is an 8 minute walk away.
Long Island MacArthur Airport (ISP) is four miles away from the Courtyard and is serviced by Southwest Airlines, Frontier Airlines and American Airlines. The NYC airports are an option, but I think JFK would be the easiest as you can take the AirTrain from any JFK terminal to the Jamaica LIRR station and from there board a LIRR train to Ronkonkoma.
Arrangements are being made for bus transportation between the Courtyard, St. John's Church and Bourne Mansion.
Besides George growing up on Long Island, once we saw the Bourne Mansion, we knew we wanted our reception there. We think you will agree.
We are working on our registry and it will be posted here soon.