At the park, there are lots of puppies too trying to provoke other dogs to play. If you have safe yard at home, look for a nice bouncy toys or balls he can chase. Our George loves this sturdy ball that can be filled with treats inside, see here StarMark Everlasting Fun Ball Medium 2.75"
It really makes our George occupied for hours chasing the ball around and getting some treats. You may keep your pup away from your older dogs to prevent any fighting or snapping habit between them, always supervise them.
"Did you ever walk into a room and forget why you walked in? I think that is how dogs spend their lives." ~Sue Murphy