Next headline: "Save the kid _and_ the dog from a 70m deep, 35cm wide hole"

Because 70 meters isn't challenging enough?

"Any old winch would have worked but we decided to go with the helicopter for flare."

Heli, because OP mentioned the surrounding soil was soft and muddy, landslide, etc. Also for flare, obvs.

Use dynamite to open the hole a bit :D

midget then

seriously 35cm ain't that small, i am almost 2m tall and when checking those Vietkong tunnels i could fit in secret hole in ground which was slightly bigger than my shoe

i am pretty sure for 35cm you could go with normal skinny adult, no need even midget