The Watkins Glen KOA is excellent. If you can get on the lower loop they have paved sites that are pretty nice. Red Ponds is nice but can get pretty buggy with all the ponds around the campground. The access to the Erie Canal is great with a bike path that can take you more miles than you would probably care to go in both directions. Letchworth park is worth the trip but the campgound has very limited hookups.
Enjoy your trip to the Finger Lakes. It's a special place with lots to see and do and some pretty decent wines can also be found there.