Well...there's tons of stuff to do in New York.
Over spring break, I went to NYC for a day. We went to
"Top of the Rock", which is where you get to go to the newly opened observation deck at Rockefeller Center. Also, we went to Canal Street in Chinatown to buy some knock-offs, if you like that. I got a "Rolex" for $36 there. We also considered going to the
Empire State Building, where they, too, have an observation deck.
The UN also has tours, but I have heard many good things about that. But it really depends on what you're interested in.
Also, there are some good restaurants. A place that I like is called Jekyll and Hyde. There's one at 6th and 57th and in the Village on 7th ave. I've been to both and I prefer the one in the Village much better.
Of course, there are some neat stores in Times Square and Rockefeller Center. If you like sports, I know that
Yankee Stadium offers tours. If you plan far enough ahead (depends on when you're going), you might be able to get tickets to a
Yankees or
Mets game, or maybe something at
Madison Square Garden. Also, if you like art, there's always the
Metropolitan Museum of Art, if you like art. And you could maybe get tickets to a show at the
IMAX Theater at Lincoln Center. They have some cool films there sometimes.
For your friend's son, you might want to check out
ESPN Zone. It's true that they do have these everywhere, but it's really cool to be able to eat your dinner while looking out over Times Square.
Mars 2112 is a fun restaurant for kids. It is Mars-themed, and you take a "shuttle ride" to Mars where you eat your dinner. The food isn't the best, but it's a fun place for kids.
The Nintendo Store also just opened recently, and that's a cool place. It's right in Rockefeller Center, so you can also go to those shops while you're there.
You may also want to cross the border and go into Jersey for a day to visit the
Statue of Liberty (yes, it's in New Jersey, not New York). There are some tours there that do leave from the city, though.
Circle Line cruises around Manhattan are supposed to be fun, too.
I hope that was helpful.
Have lots of fun on your vacation. NYC is a really fun place.