What do you get for a somewhat precocious three year old for his birthday?
My brother suggests, for his son Griffin, "...his own key set if you want to get creative. He loves real keys."
I considered the gauntlet thrown down. Digging around electrical safety / contractor sites, I found a set of lockout padlocks - color coded, differently keyed.
And since there are two sets of keys I'll make sure to put a second set of keys together for daddy, just in case Griff decides to lock something up secretly and daddy does not discover it until later.