M.C.
I have been looking int stranger safety advice to teach my 3yo.
One thing I like is teaching three types of people... "Green" people are people she is 100% secure with... Mom, dad, and other immediate family. She can interact with green people however she wants.
"Yellow" people are people she is aquatinted with... Teachers, coaches, family friends. Yellow people are ok to talk to, but never keep secrets for them, never go anywhere with them without the permission of the green person in charge of her, etc.
"Red" people are people she doesn't know. She has to get permission to interact with red people. She is allowed to smile at them and maybe wave, but no touching or talking to them until after Mommy acknowledges her desire to do so and gives her permission.
I think the idea needs some tweaking, but it gave me a good place to start making my plans from. :)