While it sounds like the OP has decided not to venture into Manhattan, I do want, for the sake on an accurate historical record, to debunk the ridiculousness of this statement. With a six-hour layover, the OP could easily spend 2-1/2 (assuming traffic and other delays) to 4 (if everything were to go smoothly) hours in Manhattan. I can understand not wanting to do it, especially with luggage, but a lot can be accomplished in that time: a wonderful meal; a visit to a museum; a walk along the High Line, NYC's new must-see public space; a walk, hansom cab or pedicab ride through Central Park (at the request of my 9-year-old daughter, I did a pedicab tour of the park this past weekend and was surprised how much I enjoyed it and how much I learned); relaxing in a lounge chair in the middle of the newly-closed-to-traffic section of Broadway in Times Square; or even a Broadway show if timed properly.