Wife worried about depth of pond and grandkids falling in

I have a small pond 650 gal with a depth ranging from 0 inches to 30 inches
at built in drain. It is raised about 18
inches above ground behind a retaining wall. I have just goldfish and lots
of plants. I built it with a 6 inch plant
shelf all around. I have lost a bunch of fine fish to Blue Herons and
racoons have torn up my plants. I have since installed
a scarecrow motion sensor sprinkler which seemed to work fine except that it
used a LOT of water (my water bills
were tremendous). I also tried an electric fence all around and it works
well also, but doesn't look too good so I
reverted to the scarecrow. Now my question: I would like to weld a rebar
grid (4-6 inch spacing) together and
place it on the plant shelf so you couldn't see it really unless you are
right on top of it. I would make it in sections
so I could remove it for maintenence. It would satisfy my wife's anxiety to
know the grid was there and the water would
effectively be only 6 inches deep in case one of our grandkids or neighbor
kids fell in. We have no fence and our yard
is open to a public greenbelt area which kids use all the time to play. Is
this a viable alternative? Should I paint it with
epoxy paint to keep the rusting metal from fouling the water? Would the
rusting metal harm the fish or plants?
Sorry for the long post, but I need some help with this one. Thank you
kindly for time and thoughts.

Chumley