After seeing the damage highlighted in the news I would not worry too much, airports and a lot of the mass transit should be back in action by the 17th. It may take a fair few weeks to get everything pumped out and back to normal, they will also have to inspect the tunnels and subway system for flood damage.
As tonty says the media does have a way of spinning the worst so that is what people expect and plan for - see they have their purpose. It is good that so many people took note.
I was in NYC for Irene last year and whilst nothing compared to Sandy, the new yorkers made the best of it. There was a hurricane party at the local Irish pub and I spent a good few hours there whilst the rains came down heavily outside. I would expect a similar attitude this time around too, pick themselves up and move on.
Precautions were taken (no Day After Tomorrow scenario) and all in all I am sure you will have a fantastic holiday. Enjoy it 8D y)