Everyone has been quite clear that the CM has broken a basic rule. Nobody is denying or trying to defend that. She absolutely must correct this, but there are better ways to achieve this than by a complaint from someone outside the situation. As has already been suggested, the best next step would be to tell the parents of the children concerned and let them make an informed decision on how to proceed.
But the idea of an increased risk of abduction is pure dramatic fantasy. The OP knows the children are being safeguarded by the caretaker who, in order to work there, will be a reliable and suitable person with all the necessary checks made. Yes, it’s still a breach of regulations, but it’s not a significant safeguarding risk in real life.
So it’s perfectly reasonable to question why the OP is so eager to report the CM, with whom she has absolutely no connection, for a breach of the rules whilst at the same time defending her own child's school which appears to exercise no control over who can access the entire school.
Moreover, she seems determined to pursue a complaint regardless of the possibility that it could result in leaving other families with a sudden and complete lack of childcare.
However, there really is no need for the OP to respond, as she has already answered the question of motivation, today on another thread, in which she admits, in her own words to being "a bit of a control freak". It is clear she has had one bad experience with one childminder, which is a real shame. She also has a vested interest as the erstwhile employee of a nursery company. She seems quite set upon putting others off using any childminder's services, and disrupting this particular CM's business, irrespective of the effect that might have on other families.