Kid and parents go on a trip in a Winnebago to grand canyon. Moms on camper and breaks go. Dad jumps on camper to stop it from rolling off side of grand canyon. He fails and him and wife die. Kid rushes down canyon side to help them. But they are dead. Now he needs to get help, but cannot get up canyon. It goes on as an adventure against animals and nature to find his way out. It's from 70's or 80's. Please help

They're in the Australian Outback.

The Earthling (1980)
Starring William Holden, Ricky Schroder
IMDb synopsis:
Patrick Foley has been on the move all his life. Tired of drifting and terminally ill, he wants to spend his last days in an isolated Australian valley where he grew up. On his difficult journey, he meets Shawn, a desperate city-boy whose parents were killed in an accident in this remote, inhospitable territory. Being unable to accompany the boy back to the civilized world, he reluctantly takes him with him on his trip to that valley and teaches him in a rugged way how to survive.

The Earthling (1980) - IMDb (http://www.imdb.com/title/tt0080671/)