Follow if necessary, don't chase. Chase is a game puppies love to play!

Do make sure you have enough safe space around you. 2 Miles is extreme and he should never have the patience to chase something that far. Having said that, a lot of this is new to him so there are lots of exciting smells and things to investigate. Keep the recall in check, don't let him wander too far just like you're own babies and a dog's own puppies. Use his command to keep him close, try to spot those distractions before he does. If things do get a bit much like you see a pack of 10 greyhounds entering the park, put the leash on just to be sure. (Happened to me during a client phone call last week Luckily it was them who were badly behaved, mine just investigated and avoided)