By the way, it's not your 10-year-old you have to worry about, it's his friends! A secret club room with ladders and hatches and knobs and dials... yikes. Waaaaay to tempting for young male minds. In one of my threads I explore ways to store my pool chems. I can trust my kids around them, but I lock them up for pool parties. There is an inverse principal involved that has led to who-knows-how-many pool-related accidents: the more parents there are at a pool, the less anyone is watching the kids!
If need be, I can screw the deck cover shut. It becomes a trade off of security vs. convenience. I'm planning on adding a remote switch to manually turn on the pump, so I can turn it on when adding chemicals without needing to enter this room. At that point I'd only need to enter to backwash the filter, and in general check on things, which should be every couple of weeks at most.