By having a chat and asking an adult not to molest your children, you are very likely offering a pedophile a free crack at someone else's less well-attended kid. In reality, people who molest children are deeply sick, almost certainly not restricting their attention to your children, very likely have accosted victims before this one, and will very likely go on to commit further offenses.

If one of my neighbors saw something like this happen and let it slide, I'd be absolutely furious with them.