A couple of things:
1. Have you taken a look at Section 3 of ACA's Atlantic Coast Route?:http://www.adventurecycling.org/routes-and-maps/adventure-cycling-route-network/atlantic-coast/
Conshohocken is near KoP, and the route goes through D.C. with an option to avoid Baltimore and then on to Richmond. Section 4 continues south and comes somewhat close to VA Beach.
2. The only way to actually ride your bike from NYC to NJ is via the George Washington Bridge, which is up north in Manhattan. All other bridges are off limits to bikes. That can be a very difficult part of the world to navigate by bike if you don't have experience. New Jersey is the most densely populated of the 50 states and northeast New Jersey is the most densely populated part of the state. Making it all the way to KoP in 100 miles seems like it would be tough, but if you have a route mapped out I am willing to look at it.
Fortunately, there are several train options out of NYC. You can easily get as far south as Trenton, NJ via New Jersey Transit. You can also get as far west as High Bridge, NJ. Section 2 of ACA's Atlantic Coast Route has a NYC spur that utilizes a train line between Summit, NJ and NYC. There are also ferry options between Manhattan and places like Hoboken. Without local knowledge and experience, I highly recommend taking some form of Public transportation out of the NYC area.
Every year my local club does a ride from New Hope, PA, which is on ACA's Atlantic Coast Route, to Brooklyn via Manhattan that goes into Hoboken, NJ and reaches Manhattan via a ferry ride across the Hudson River. The ride is held the Sunday before Labor Day. To do during a weekday would be suicide since, among other things, it goes through the Port of Elizabeth & Newark, which is usually non-stop speeding truck traffic. (The Port is empty on Labor Day weekend.) There is a way to take a train beyond that point, however. Still, that would leave you with some miles to get to New Hope.
Finally, March can be iffy depending on the type of winter we have been having. It could be decent or it could snow, especially if you are talking about early March.
Have I confused you enough?