There are many things wrong with the Jehovah's Witnesses...many, many things. But this is not one of them.
Just as being an ex-JW does not automatically make you a "mentally diseased apostate," being a JW does not automatically make you a person with questionable morals.
Good people get caught up in this religion. Good people are still within, many struggling with trying to get out. While there, most do their best at being their best. And many with no intention on leaving aren't any more a danger to your child than the good, faithful priest and kind nun in a Catholic parish who are not involved with child molestation (and in fact fighting against it).
Most of us here were once Jehovah's Witnesses. When we were kind to a child, was that due to some morally questionable desires we had? I doubt it. Regardless of how much we did or didn't believe in the doctrine, most of us were not a threat to children. Human nature generally moves us to act as protector and educator, not predator, even when it is not our own child. That is why sexual child abuse is so horrible becuase it goes against our basic human instincts regarding children.
Regardless what Jehovah's Witnesses believe or teach, none of this makes them any less human. They may regard us ex-JW as less human or "mentally diseased," but we will not be the same in kind. These are people, you were once one of them, and we are not so far removed from one another as we often like to think. Don't throw the baby out with the bath water. Condemning genuine kindness in others condemns us when we act the same.
Understandably many are angry and greatly hurt after leaving the Watchtower, but like everything else, we need to keep our emotions in check. When we start seeing everything the Witnesses do with suspicion, that is a signal we may have let things go too far. Emotion can only take you to a certain point and negative feelings can't be your master. Use common sense and common decency.
And stick to facts instead of calling each elder who shows kindness to a child a potential child molesting pervert.