Well PTT many can probably provide their own weapons!
A small scale training course with their local police should be enough, if they are retired police they should know a fair bit already, just some refresher training required. I guess in some situations off duty police could take part to hence they would likely have the already required training. With the need to vet them, if retired police it should be fairly straight forward, retired military a little harder.
No, no system is 100% perfect, but atleast my ideas would increase security for the children AND allow gun owners to keep their weapons. Simply banning things you don't like is not really a good direction to take a so called free country in.