I am assuming you are going to New York City. The first time I went I stayed in the Marriot Marquis in Times Square. I went back a few years later and stayed in the Da Vinci it was on 57th, I think, Near the Ed Sullivan Theater. It is a town made to walk. We went to see "Wicked", Statue of Liberty, Ellis Island, Yankee Stadium we were able to see a game while there, Shea Stadium, Coney Island, China Town, Little Italy, Wall Street, the Twin Tower site, Battery Park, Central Park. It was funny one day we came out of the subway, and my DD and I were standing there making sure we knew where we were and suddenly realized we where at the Court House they show in "Law & Order" all the time. It was a Saturday so it wasn't busy. We drove by the New York Public Library, the United Nations and so much more. One of the days there were a bunch of second graders lined up to go into Carnegie Hall with their records (flute-a-phones) and I laughed and said, some day they will be able to tell their family they performed at Carnegie Hall.
If you go during the holidays you definitely want to go to Macy's to see their window displays and the other shops around.
So it isn't so much what we could recommend - it is what do you want to see? I went to the garment district without my daughters because neither one sews. They have shops with nothing but buttons & trims. Lots of very fancy fabric but I never did find plain cotton - but I was so exhausted by then I didn't look real hard. After all we do have a garment district in Los Angeles. And I had already been to Salem MA.
Make a list of what you want to see and get a map of the city and then plan what to see when. There is a site seeing tour bus, not sure what it costs, but I think when we went it was $28 a day. But can't remember if that was for both of us or each.
I love that city and would go back every chance I can - unfortunately my husband doesn't care to go, so that is why God gave me my girls. They love to travel with me.