We just did NYC in April.
Disney store moved to Times Square, and I'm sorry to say I liked the old store better, it was bigger. My daughter liked the Toys R Us in times square, they have a ferris wheel inside. American girl place if you have a doll collector.
Loved!! The empire state building at night. We ate downstairs at the brewery, DH loved it, daughter liked it too, and went up to the viewing area 45minutes before dark, line moved very quickly.
Have done statue of liberty with kids and ellis island, OK but not the favorite.
Central Park has lots to do, look online and get a map if you are going to do this.
Chinatown and little italy were fun. The great noodle house was a real bargain for lunch $15 for the three of us. We ate through there.
We always see a show when we go to NYC. Mary Poppins was wonderful.
Rockefeller Center and magnolia bakery(although I prefer the magnolia bakery location on Bleeker st)
The NYC fire dept museum was very good. We found an irish pub for lunch near there that had excellent and reasonable food.
These are just some of our favorites.
We went to washington a few years back and be advised that when we were there all museums and monuments closed at 5, so may be a short day if you are doing a day trip. You may want to check closing times of the things you are interested in.