All you have to do is be more clever than them...

When my son was 2 I noticed that I would come home and my beloved CARVER system would be powered on.
Solution: put everything inside a fully-enclosed entertainment cabinet. So there!

2 days later... system found turned on again.
Solution: built "barrier" made out of lattice.

10 minutes later... system found on.
Solution: ran to hardware store, bought drill, lock set, drill bit, etc. and installed lock on entertainment system.

2 days later... system found on, had to ask my son where he left daddy's keys...

That led to the extreme solution of removing the fuse from my amp and unplugging everything between "sessions". (Daddy was not very patient back then)
2 weeks later, had to send amp to CARVER repair to get the fuse box fixed. During the waiting period, my son lost interest and found other toys.

Anyway, roll clock forward 10 years. I now wish my son would want to play with my system instead of playing video games all day. In retrospect, I guess I missed my chance...