We went from Northport to Atlantic Highlands in an easy day, riding the current all the way.
There is a great Andriod ap that gives state of the current at any time called Currents.
If you don't have AIS, there is an AIS ap also, but it isn't always up to speed.
make a security call because Hell Gate is a blind turn. We found the area just east of Hell Gate was a bit more of a concern as you get pushed around a bit. But all in all it was very easy.
Try to avoid the Battery at rush hour or the ferries will be a bigger issue. We slipped behind the island SE of the battery to avoid the traffic on our way south