We probably went 5-6 miles. Enough to get out and get a little sweat, but not too much for a first ride. Glad we turned around when we did... we still felt good, Bay was getting a little winded when we climbed any long grades.
Riding on that greenway was neat. Bay was a little jumpy, like he thought a deer would leap out of the trees at any moment. ;~D
That looks like it would be a nice place to take a lunch and a picket line. Ride awhile, break for lunch, then ride back.