When I was a little girl, my parents and I rode the motorcycles up to Bear Mountain all the time, but I haven't been in years and years (other than for a wedding at the Overlook Lodge a couple of years ago, memorable both because it was a beautiful wedding and because it was the site of my terrible, horrible eye incident). I have all sorts of memories of my dad and I rolling down the big hill like logs and playing Aerobie (remember those?!) on the lawn, and have been wanting to take Kendrick and Indy there for awhile now.
If you're in the NYC area, I highly recommend giving Bear Mountain a try for a day trip: it's only about 45 minutes outside the city, is an absolutely spectacular drive in the fall, and is right next to Cold Spring (another of my favorite day trip towns), so you can hit up both in one go.