Don't neglect training of your kids. With all due respect, it appears that you might be looking for a foolproof safety system in a firearm. That is just not gonna be something you can count on. A safety is a mechanical device that can fail.
A couple threads well worth looking at:
https://www.indianagunowners.com/fo...-home_defense_gun_safety_-_advice_please.html
https://www.indianagunowners.com/forums/general_firearms_discussion/5055-do_your_kids.html