My info may be very outdated but there should be an airport bus from JFK directly to Newark Airport, where you can rent a car or be picked up. If this bus has been discontinued, there should still be airport busses between JFK and Manhattan's Port Authority Terminal and between Port Authority and Newark Airport. Perhaps there's a bus line from Port Authority with a stop in Jackson or near it. (check out Peter Pan/Trailways) Quite a few places in NJ are served by these bus lines. Can your parents check this out from their end? I just hope you're not traveling now, in this blizzard.
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