I have a monster of a 3yo. Complete terror to most things. Even my upper cabinets are locked because he climbs the counters and gets things from the uppers. Besides the obvious one of keeping the tank cabinet locked (I use the magnetic locks too) and tank chems locked away also, I do more like attach smaller tank stands to the wall, you'd be surprised how little force it takes to shake a small tank on a stand. I use L brackets and screw from stand to wall, using anchors as needed. I have a 29g, 15g and a 13.5 anchored to the wall, but it's not needed for the larger 75g. That's heavy enough to keep planted.
Also lids to prevent things going into the tank. Even just toys by accident, I left the back cover off my 13.5 once, the chambers were promptly filled with hot wheels.
Also think about water changes. Open buckets are like a magnet, the dirtier the better. So you might need to re-strategize if you use buckets.
Overall, other than minor things, the reef should be protected from the kid. At least in my case, lol.