Don..welcome aboard and pay no attention to Grandma Dawg! (G) You gotta get your feet wet sometime and if you pay close attention to the weather and don't try to push anything you will be fine. You have a good boat and if you've been singlehanding a while now in fairly protected water...you know how she handles and are familiar with her nuances. I do have a couple of suggestions though.
1. Don't leave it too late. I would be heading south at the end of August rather than later.
2. Choose a more in-shore route on the first part of your trip to the Canal. The likelihood of bad weather and fog is higher there and there are plenty of places to duck in and it only adds a little to your trip if you don't have to head in to port.
3. Consider going offshore from Greenport LI to Norfolk instead of the coastal route through NYC and the Jersey coast. If you get a 3 day good weather window you can be safe and sound in Norfolk and a daysail away from the Rappahanock and have had a REAL open water passage that is not difficult. The route through LIS and Hellgate in the East River and along the Jersey coast is certainly do-able but will require more time and does not give you a true blue water passage under your belt. Of course...if you want to sight see...that is fine but with a couple of extra crew an offshore end- of- summer passage could be nice.
4. Equipment wise you've made some good preparations. Consider a radar...not just a card..you'll be in shipping lanes. Get third GPS and put it in a box with lots of batteries. I do not see an EPIRB or Liferaft on your list of equipment. What is your plan if you hit something or get knocked down and the boat starts to sink? BoatUS and other places have rentals suitable for short trips.
Good luck and welcome to the board.