Autumn is my favorite time of year. The colors don't seem to be as brilliant as other years, but still nice nonetheless. A couple of weeks ago, we took a drive on Henry Hudson Drive, which is a road that cuts through a portion of the Palisades Interstate Park, right near the Hudson River. What a great road. We had gone in the afternoon and by that time, the sunlight was not direct so the colors were kind of drab-looking, but still nice. A good time to go is on a sunny morning.
Last weekend we went to Piermont, NY and had another great day. We browsed through a small farmers market and walked around, enjoyed the colors and sights, had lunch.
This weekend I had planned on going to the Cloisters, but it looks REALLY cloudy outside - not sure about that one.
Someone in this thread had mentioned making reservations at the Cullinary Institute. Great place. I haven't taken my in-laws, but my wife and I had been there once maybe about a year ago. We were very impressed. The food was outstanding. My wife and I struck up a conversation with our waiter and asked about his schooling there. We were surprised to hear that the most difficult course he took was the one on wine - what with having to know the different grapes, countries/regions, to know which wine goes with which types of food, etc.
My in-laws have already done most of the touristy stuff on previous visits and haven't expressed any interest in re-visiting those places - so the search continues