We taught our children a password for if someone collected them from school or elsewhere when they were not expecting it. At 37 DS3 still remembers it. It was never necessary but gave us peace of mind.
Recently the subject came up with DGC, aged 5 and 3 and they knew about not going off with someone they didn't know but didn't know about anyone telling them not to tell Mummy or Daddy. They then told me that Mummy says if they tell Daddy they won't get any sweets. So what is she doing they mustn't tell Daddy? I find this very worrying as she insists on knowing every detail of what they do with Daddy. When I wouldn't give one what he wanted he said 'I'll tell Mummy'. I told him to go ahead!
Things you learn from Watching TV (light hearted)
Disappearing contributors - part 2


. When you're worried about something you home in on all of the news items [of which there are many]. When my children were small it was all talk about nuclear war; I went to see my doctor because I was so worried and he just said 'do you get out much and meet people; if not, start doing it'. I thought at the time it was a daft thing to say; in retrospect he was right.Once you have children and grandchildren the world suddenly becomes a very scary place; it's just a case of dealing wih that fear I guess.
. but to get back to the OP, these awful people have always been with us, but you mustn't blight your life, and your grandchildrens' lives by seeing paedophiles in every public place. Also, it is a sad fact that most victims are groomed by people known within the family group. You must not let this worry take over your life ( I know what I am talking about, I could worry for Britain).