Be flexible with dates
You will need a couple of publications: chart books for Newport to NYC and for the Hudson River and Champlain Canal. Also you should get the appropriate cruising guides - the latter will have all of the marinas listed with contact info. You can call to find out when they open. I would imagine they will be all open by May.
The canal does open May 1 but that is only if the conditions allow so you need to be flexible about this. Also, it is not rare for the canal to open and then close again if water levels become too high.
A final consideration is where you will take your mast down and put it up again. If you are comfortable doing it yourself you can take it down at the Castleton Boat Club south of Albany. If not, there are a couple of marinas further south that will do it for you (I forget their names since I always go to Castleton). There will lots of options for getting the mast back up in Lake Champlain but I have not ever done it there.
Finished the circumnavigation in early February in Grenada. Have to work on a book project for the next several months so the boat will be waiting for next year.