Just as I may have been wrong about his location and whether it is okay to call 911 for non-emergencies there, do not assume that every area of the country wants 911 used for all real-time situations. In the busy metropolitan areas that I have lived in, 911 was reserved for life-threatening emergencies because other calls tend to flood the system; a flooded system means the heart-attack victim's call doesn't get through fast enough. A fleeing thief is not usually a life-threatening situation and can be handled by calling the police (which IMO ought to be a similar easy number to remember like 611 or such).
Even without an easy to remember #, it is simple to add the local emergency numbers to your cell phone.
In this post, the guy may have antagonized the gangster into trying to run him down, further endangering others over a measly phone. All he had to do was call and/or discreetly follow and get the license plate #.
Kids, that's a different matter. Getting a kid to call anyone is a big step. I'd wait till they much more mature before worrying about the distinction between police and 911.