Definitely a highlight of my trip was booking this bike tour around Central Park. Tony did a great job showing my wife and I all the great sites around the park and gave us a bit of history on the park. He also gave us time to take pictures and some of the nicer locations. I highly recommend this tour.
Tip 1: The roads are very busy with fast bikes and runners on the weekends, but there are no cars to deal with. There are much fewer bikers during the week, but then you have to contend with the cars. Pick your poison.
Tip 2: There is a easy/moderate bike ride, but the hill on the North end of the park is fairly demanding. A couple of the people in our group had to walk their bikes up this hill.
Tip 3: Have a delicious (and a bit pricey) breakfast at Asiate at the Mandarin Oriental before or after the tour for some of the best views of Central Park.