Right across the street from the wedding venue. One of the great art museums in the world, and a regular site for our date nights.
So much to do. Beautiful walks (one of our early dates was looking for all of the waterfalls in the park). The conservatory will be georgous in June. You can rent boats to go out on the lake. Belvedere Castle is nice to visit for the views. The zoo is also nice (although the Bronx zoo is better).
A beautiful memorial. The museum is a moving tribute to the losses on 9/11 and the city's ability to come together in the face of tragedy.
If you like baseball, the New York Mets will be playing the San Diego Padres over the weekend of the wedding. Citi Field is known for having some of the best food options of any baseball stadium.