I did do that once -- I was heading to Europe for two weeks, out of EWR, and i had this idea that the car would be safer if I parked it on the street on S.I. near the home of a family friend.

So, park the car. Walk to bus stop with luggage. Take bus to St. George ferry. Take ferry to Manhattan. In my case, walk to another bus stop, wait for bus to EWR... ah, the heck with it.

This guy's got two small kids; the hassle factor goes way down if he can just ride the train from the hinterlands straight into Penn Station. And the Amtrak lots in NJ are safe and no, no permits required; this is what they're there for.

As for valet-parking the car in Manhattan: a week of that action will probably come to more than $200.