Just had another thought, and the kids, if you are taking any, should like it. Manhattan is an island so there are lots of ferries. Take the Staten Island Ferry, or the Circle line, which will take you right around Manhatten. On a hot day, it will be cooler on the water and you can tick the bridges off as you go around. Take a packed lunch ( nowhere does sandwiches better than NY. Eating a Pastrami on Rye while sailing along is a wonderful way to spend the day ! ) Watch out for the Cable Car over to Roosevelt Island...yes, a cable car in NY !
When I was last there I took the train over to Brooklyn and then walked back into Manhattan over the bridge, Marvellous views !
Go to Ellis Island, where the NY Immigration was based until a few years ago. Millions of immigrants were processed there before being allowed in America proper.
https://en.wikipedia.org/wiki/Ellis_Island
I wish I was coming with you !