I'm of the opinion that the lock should be mechanical and simple - Simplex, for example. All other considerations would be secondary.
It's not meant to be secured against actual theft ( unless that's what you meant by the grandkids!
). For something that's small enough to easily be carted or even lifted away by one or two people (or, for example, the ShotLock AR Solo-Vault, which can essentially be leveraged or just ripped out of the wall), I would prefer the "safe" actually not being displayed outright - to at least hide it from sight.
As a deterrent mechanism against unauthorized access, all I need and want is just that: a visual deterrent - so that the firearm remains quick to access in emergency situations and under duress.
For (a) handgun(s), I would use the same considerations, a simple mechanical lock. I'd want the "safe's" internal dimensions to be big enough for me to store whatever handgun(s) I choose in a quickly don-able holster: this way, I can just reach in and go (without worry of potential interactions with the trigger). From there, either rip the holster off and engage or alternatively (and preferably) quickly clip-in the holstered weapon (even if you don't usually wear a belt around the house, there's now excellent hardware that can allow an IWB holster to gain secure purchase on the waistband; if your wife prefers dresses or other one-piece attire, this may need an extra bit of work....maybe an Unity/Vertex CLUTCH?...that would also have the ability to be staged with even more tools, provided that the "safe" has enogh interior volume).
