I've recently had some retaining walls installed and now am hoping to install some "temporary" fencing along the top of the LOWER level (see below) primarily to deter the family from getting to close. Options I've seen include basic picket fencing (metal or wooden https://www.bunnings.com.au/rapidfence-2200-x-41-x-1200mm-black-blade-picket-fence-panel_p0438319), wire fencing and posts, or even glass pool-side-type fencing. I can't dig behind the wall: we have SUPER hard rock and digging and concreting posts is not an option, plus there isn't much space anymore). Plus I plan on removing the fence in a few years once family has grown up enough to stay away from the edges.

Can I simply bolt posts into the top of the wall? Would it be better to bolt to the front? There's only 50-100mm space on the rear of the wall to bolt to the back.
I'd love some ideas, or tips, or further advice.