How do i get my dad to play with his grandson early in the morning?

Complicated issue: First feed grampa well, entertain him with the delightful antics of his grandsons and conversation with his son & daughter-in-law. Then make sure gramps is off to bed at a decent hour so he can be fresh in the morning with the little guy. Good luck!

How early is early ?: If your son awakens before you want to be up, use age-appropriate behavior techniques like ignoring his early AM waking rather than expecting your Dad to get up & reinforce your son's behavior. If you need your Dad to care-take your son while you get ready for work, ask him to do so directly & politely. If he declines, ask him if anything would change his mind, but accept his answer as final.