I'd like them to be in prison.I have a wife and two kids and for sure I'd like rapists and child molesters to be unarmed...
If they want guns, they can get them. The law only increases the risk to them if they get caught with a gun. If the criminal doesn't think a gun is much of an advantage, he'll use a knife/screwdriver instead. Rapists generally depend on the threat of force rather than the use of force. If a victim isn't going to resist an attacker armed with a gun, will that victim resist an attacker with a knife? I doubt it. What difference does it make whether a rapist can legally own gun or not?
If the dynamics somehow changed, and having a gun was a significant advantage, rapists would no longer care about the minor increase in risk from carrying a gun around, and that's what they'd use, if they don't already.
As for child molesters, the disparity between an attacker and a child is usually so great that it doesn't matter whether the attacker has a gun or even a knife.
It seems to me that you're falling into the trap of viewing guns as some terrible evil. They are formidable weapons, but they have weaknesses. In close quarters, most martial arts experts seem to agree that guns are easier to defend against than knives. Rapists not only have to confront their victims at close range, but they don't usually want to shoot or knife their victims. Guns lose a lot of their advantages in those situations.