There are quite a few clubs if you just take a cab to Gansevoort and walk around. I can't say I'd recommend a rooftop party in January in NYC. It'll be freezing cold. Just don't get suckered into buying a table.
During the day you can check out the
hi line. It's essentially a very nice park built on an abandoned elevated railway. I do that stuff with my wife but with a bunch of dudes, you may want to skip it.
A tip for any visit to NYC... stay as far away from Times Square as possible and don't you dare set foot in a chain restaurant.
El Rio Grande is a tex/mex place in midtown that I love because the food is good and the Margs are the strongest around. I go there after work quite often but there isn't much of a "scene" until the deck opens in the summer.
Burger Joint in the Parker Meridian hotel lobby is one of the best burgers on the planet. There is no sign, only a glowing burger hidden in the hotel lobby. It can get REALLY busy but you should give it a try.