My father in law is 84 and rides his bike 5 miles once a week. Not like what your doing but pretty good for an old man. Good to teach the young kids some good old fashion exercise.
it is great exercise (very light cardio, if your on level ground)
me and the wife were discussing the boys weight and i mentioned to her i used to be chunky until i hit highschool
we didnt have school busses and i had to pedal 6 miles one way, 5 times a day
that knocked the pounds right off
(by the time im met the missus, i was 6 even and 175 pounds)
so i figured, no reason to wait for him to get there, might as well get started now