Originally Posted by
dinosims
Remember to add in time for getting your baggage, getting out of the airport, getting a rental car, etc (which would be more in JFK also due to it's size and traffic in NYC).
The OP is looking at trying to do the Whitestone and GW bridges at 6:30pm by the time they get their bags, monorail to the rental car and get the car. Traffic at that point has the potential to be pretty bad. I would add an hour to the Google drive times for the traffic to get over to I-80 in NJ.