Personally, I would call ch ild protection. You can remain anonymous. She will never know who called...because it could have been anybody!
I am sure that you will not like the idea of doing this.....
But, remember this is about the HELPLESS CHILDREN. It is not about your welfare, or even the parents, at this p oint.
We all have a social responsibility to protect children. I feel strongly about this....
At least, that is what I would do...