Is my daily bike route enough exercise for a 60 year old?
Enough for a little expertise - yes, enough to train for a 100 mile ride, no. 

If you are just looking for some healthy exercise you can gradually increase distance and/or speed and back off if you over exert yourself. 

If you are unused to exercise or are not currently in great shape, you should consult a doctor before trying anything significantly harder than you are doing now.