Walkabout (1971)

A privileged British family mother, geologist father, adolescent daughter, small son live in Sydney, Australia. While on a picnic one day, the sibling get stranded in the Outback by themselves, not knowing exactly where they are.

They only have with them the clothes on their backs their school uniforms some meagre rations of nonperishable food, a battery-powered transistor radio, the son's satchel primarily containing his toys, and a small piece of cloth they used as their picnic cloth. While they walk through the Outback, they encounter an Australian boy who is on his walkabout, a rite of passage into manhood where he spends entire months on his own living off the land. Their largest problem is not being able to verbally communicate. The boy does help them to survive, but doesn't understand their need to return to civilization, which may or may not happen based on what the Australian boy ends up doing.