We chose to take the hop on/hop off bus ride, visit the Statue of Liberty and Ellis Island, go to the top of the Empire State Building, and check out Madame Tussaud's museum.
Adult tickets are $87.99 and tickets for children are $63.99. [They also offer a similar savings for Boston.]
https://www.costco.com/New-York-City-Choose-4-Explorer-ePass.product.100170110.html