I did this trip last week from Atlantic Highlands to Catskill. This trip is too ambitious for inexperienced sailors in a small, slow boat. While not directly on your route, we went from Catskill to Troy, a 34 nm trip that took 7.5 hours because of the tide and timing. Our speed through water was consistently over 6 knots, yet our average speed was just 4.5 knots over ground.
Can it be done? Yes, but not in three days. Expect to find currents in the 2- 2.5 knot range sometimes with you, more often against you. Because this is an estuary fed by a river, the ebb currents are stronger and longer than the flood currents. On the up river trip the tides will be working against you more than helping you.
The East River can be a joy ride or a ride from hell. Even with the current with you, expect swirling eddies, 1-4 foot standing waves and lots of noise and distractions. On our last trip down the river in September, we had motorcades with flashing lights running up the FDR drive, helicopters, high speed ferries and an airplane taking off with subway trains running on the bridge, on top of the usual cacophony of NYC. I had a ball, not every body does.
Catskill is kind of a neat town trying to remake itself. On a Friday evening there were people on the street with the bars and restaurants filling up. It has a cocktail bar, Hemlock, that was recently rated as one of the top 10 cocktail bars in the country. And a great ice cream stand with homemade ice cream and an enthusiastic owner. I'd go there again.
Lest I be characterized as a Davey Downer, I do want to encourage you to cruise and explore our waterways, the joys and benefits are amazing, the people, the places, the things you can see only from the water are worth every miserable moment you have. And cruising has many miserable moments. Start out with positive experiences. Sail to Oyster Bay, Sail to City Island, there's a great little restaurant there, The Black Whale, sail to Port Jeff or across to Mystic Seaport Museum and stay at the museum. Having these kinds of experiences behind you will make you much more tolerant of those days on the water, when you wonder "Who's idea was this any way?"
Fair Winds and Safe Travels.