We visited Times Square, Central Park (Zoo), Rockefeller Center, Flatiron Building, Grand Central Station, Trump Tower, Museum of Natural History, Statue of Liberty, Broodlyn Bridge, St Patrick's Cathedral, Chinatown, Empire State Building and the 9/11 Memorial in 2 days.
If you do not need a lot of time at each place this is doable while walking and taking the metro to the south of Manhattan.
We recommend to spend more days in New York City if you want to see more things or need more time to see and move to places.
We visited Kennedy Space Center.
If you want to learn about the space program you really have to go to Kennedy Space Center. They have enough attractions to keep you busy for a day while you learn new stuff and see real spacecrafts.
Don't forget to take the bus ride which brings you past de iconic Vehicle Assembly Building and drops you off at a real Saturn V rocket.
We visited Blue Lagoon Island.
At Blue Lagoon Island you can relax on their private beach and swim. You can also choose to do the dolphin encounter in which you will kiss, hug and dance with a real dolphin.
Included in your visit is a "Bahamian Lunch" which was not that great.
We do recommend to visit Blue Lagoon Island once but it is not worth coming to Nassau specifically for Blue Lagoon Island.
MSC's Ocean Cay is the best place to relax on your MSC cruise vacation. It has lots of beaches to choose from and enough beach shacks to get some drinks or a quick snack.
We recommend to go to North Beach because it is less crowded compared to other places on the island.
In the center of the island you can swim with a few Lemon Sharks. You don't have to worry about dangerous sharks entering these waters because they have shark nets. If you do want to swim with the animals in the ocean such as stingrays you can do this on the outer edges of the island (these beaches are not guarded).
On MSC Meraviglia you can enjoy a show each evening in the Broadway Theatre. You enter this theatre via the promenade which features a lot of shops and restaurants (these are not included).
They have a sports center, basketball field, arcade games hall, multiple pools, climbing course, F1 simulator and a bowling area on board of the ship so you will not get bored on a sea day.
Next to the regular theatre show they have a Carousel Lounge where they perform a paid show. We went to the Rock Circus show and do not recommend this one. The House of Houdini show looked great but got cancelled mid performance due to a leak.