"The smell of the Ordon children, which was on the wooden sword that you found in Eldin Province."
This scent is found just south of the entrance to the Kakariko Gorge, where the Wooden Sword, the one Link gave to Talo, can be found on the ground, smashed to pieces. After sniffing it out, Wolf Link will learn the Youths' Scent, and be able to track the scent down. The scent trail will lead through the Kakariko Gorge all the way to the Sanctuary in Kakariko Village, where all the children are hiding from the Shadow Beasts with Renado, his daughter Luda, and Barnes.
Wolf Link detecting the Youths' Scent