Frosty, cub scouts will get you hurt(G)...
Doug,my kids were used to handling guns from about the time they could cross the street by themselves, under close supervision, of course. Son may have been all of 9 when he shot my 1911 GM for the first time.
For smaller kids, a pump kept cruiser ready (action locked shut, safety on, mag full, chamber empty) and kept high, like inside a closet above the door is enough to ensure safety. Yours are more able to overcome those measures, so there's other options. I don't know about you, but the folks had nothing I didn't get into while they were away. This approach may help...
Take them shooting and let them watch as you put a round into a pumpkin, 2 liter soda bottle filled with water, or other target that will explode dramatically. Explain that the gun is a marvelous tool that MUST NOT be misused, and that the stuff on TV is myth and illusion. Let them pop off a few 22 rounds, SAFELY,and let them handle firearms enough(Under supervision of course) to take the mystery and glamour out of them. Mine knew they could examine any gun in the house if they asked permission, and permission was ALWAYS granted.
I believe this approach is safer and more effective than a cable lock or safe. BTW, the little handgun safes are cheap, and a good place to keep a loaded handgun. Access via the keypad is PDQ.
As for your query, I prefer the safe. Your needs may differ.
There may be some old threads on a lockable shotgun rack, or another contributor here may be able to fill you in.
As for Tazers, I've no personal experience with them. I do know they're considered Deadly Weapons in some jurisdictions. IMO, she'd be better off with a mouse gun concealed on her person. A nurse I knew long ago worked in a good hospital, bad 'hood. A PPK clone in an ankle holster was her approach, and it sounds good to me.