It's something I worry about constantly. There was an attempted abduction outside our school last year

I know it sounds ominous and scary but I went with what you said - there are people out there who want to do bad things and it is mummy's job to protect my children from bad things. So they don't go with anyone they don't know. DD (prep this year) is not to leave school with anyone other than mummy or daddy, unless we have told her it is ok (as in word her up - Grandma will pick you up today!). If anyone tries to take them, make them get into a car, or do anything that makes them feel yukky, they are to kick, scratch, bite, hit, do anything to get away. They are to find mummy, daddy, their teacher or a police man/woman and tell them they are scared.

I'd rather them scared and safe than happy and ... yeah. The alternative makes me feel ill.

Hope that helps. We've talked about it a lot.

ETA - what wysiwyg said makes sense - when we go somewhere (like the zoo, a shopping centre) I've started asking DD "If you got lost here, who would you ask for help?" and getting her to try and pick out the "safe" person. She's getting pretty good at it.