Preparations for a Manhattan to Nantucket straight through passage on the south side
Tempest made a good suggestion. One that my wife and I did recently. We have exactly the same plan as you. To start gaining passage making experience. This was to be our first overnight trip. Our goal was to sail from Staten island to Martha's Vineyard. For the outbound trip we stopped in Block Island to recover and evaluate our experience. We did 3 hour watches overnight. It took 23 hours and we were about 3 miles from shore. For the return trip we sailed straight from Martha's Vineyard to Staten Island doing 4 hour watches overnight and 2 hour shifts in the day. This took 32 hours and we were about 6 miles from shore.
The experienced sailors have already given you (and I) a lot of good advice. I would like to add Fish Pots. The closer you get to Block Island the more there are. Even 5 miles out. Some of the floats are 9ft tall with big black flags so you can't see them at night until you pass them with 8" to spare. ( scared the hell out of me).
Also don't underestimate how tired and disoriented you get at 3am. It was very tough to keep alert.
My moto for our trip was "if in doubt pick the safest option". As our experience grows so will our adventuring.