I let my 9.5yo sensible and practical DS walk across 2 roads (one with a crossing) and through the car park (with zebra crossings) to the local supermarket. It is, however, less than 100m from my house and he always goes with a list and cash.

He only gets it as a reward for good behavior and I wouldn't send him with his 7yo brother as it would be too much responsibility.

I let them walk around the corner to their friends' houses near their school, but only when the friends' mum will text me when they arrive.