Let's start in the 5 boroughs---yes, I know you said you've done things in NYC already. But have you done the following:
1. Taken the train to the NY Botanical Gardens in the Bronx? At the end of April, they are truly stunning.
2. Gone to the Bronx Zoo?
3. Played tennis at the National Tennis Center in Flushing?
Outside of NYC:
1. Daytrip to Mystic Seaport. You can get there via Amtrak. See if this interests you:
http://www.mysticseaport.org/index.c...894823B5CDBB57
2. Vanderbilt Mansion. Take Metro North to Poughkeepsie and then take a taxi to the mansion.
http://www.nps.gov/vama &
http://www.hudsonrivervalley.com/ind...d=6&page_id=56