This is an easy for ride beginner cyclists. Most of the NYC streets have bike lanes or "sharrows" and there are no steep hills. There is definitely city riding with numerous traffic lights, but no difficult intersections; and the High Bridge is a NYC landmark. Bronxville is a cute little suburban town with plenty of food options. Lange's deli is very good, but usually crowded; Il Baccio has excellent pizza by the slice as well as soups, salads and real meals (and gelato). There's a Starbuck's if you just want a snack.
I've added a slightly different route that starts on the West Side at Riverside Dr. & 97th St. https://ridewithgps.com/routes/26725383 This is an easy way up to the High Bridge. From there it mostly avoids University Ave. and the high traffic streets thru the Bronx, so it's a little more pleasant than the original route. This route is 31 miles.
cw 2/9/16, modified 1/16/18