Head back over to jack (indicated by the 'J' on the map) and you’ll catch him shooting. Once John notices the wolves, ride off towards them with your son in tow.
Your dog will lead you to a pack of wolves who’ll attack you if you’re not careful, so line them all up either with a well aimed stick of dynamite or by using Dead Eye and your high-powered Hunting-Rifle.
Your dog will be off again on the chase as soon as you kill the last wolf, so keep up with it until it reaches the snowy hills of Tanners Reach. Once your dog spots the next pack of wolves, whip out that rifle and/or dynamite again and kill them all as quickly as possible.
When you’ve killed the last wolf of the second pack, it’s time to head home to complete the mission.