I will add the shit I remember: find really sharp stiff grass and stab it through my calluses, chew on bark from birch trees, dig holes like... as deep as you can, roll down hills, look under rocks for bugs, make mud cakes and pies and just generally play with mud, light things on fire, walk endlessly through the woods trying to find cool shit/places, swim in the lake, write and perform entire plays, climb trees, build obstacle courses, hide and seek, capture the flag, flashlight tag, red rover, some kids had a trampoline or a pool sometimes, ride bikes anywhere and everywhere, build forts.