Make sure you sample the pizza. There's pizza and then there's New York pizza.
Had a great time when there on my first US visit last September. After watching Everton lose 0-3 to Atalanta

in Mr Dennehy's (RIP), I decided not to cheer myself up by visiting the 9/11 memorial and museum. A very sobering experience it was.
NYC has so much to offer it is difficult to take it in in just a few days. The free ferry to Staten Island is a must though for the best views of Lower Manhattan. Brooklyn Bridge, the Midtown skyscrapers and Central Park are also not to be missed.
New Yorkers are so polite compared to what you are used to in this part of the world it's unreal.
Would definitely go back. Enjoy!