More important than his age is his physical condition. Many dogs of this age can still run, fetch and do everything younger dogs do but perhaps for a shorter period of time. If he has any disabilities, they should be clearly noticeable.
Any stimulation, including non jarring/ low impact exercise, plenty love and talking to him. Try to pull the puppy out of him without neglecting the fact that his body has reached a point where young pup type stuff is counter productive. And always understand that extreme heat and dogs don't mix.