Aside from the legal issues, my personal opinion (and it is personal, for once) is that perhaps this guy should be given the chance.
Before I'm slaughtered for this, please bear in mind that I don't have children and nor am I a particularly paternal person! But the sentence was 4 months, not 4 years, so I'm inclined to believe that any offence couldn't have been one at the worst end of the scale. I agree that any offence is unacceptable, and particularly when it concerns vulnerable people, but 12 years is an extremely long time.
With known offenders, when any crime is committed, the police involved often have an idea of who may have been behind it. A prolific burglar or a known teenage joyrider, for example. I would believe that if the police even suspected that this man had been behind any other similar offence since his release, they'd have been on him in a second. The fact he does not appear to have committed any other offences counts in his favour, doesn't it? Even if he may just not have been caught, I accept.
I don't want to provoke hostility, so if you disagree, I understand. It's obviously your choice and you have to live with the consequences, so whatever you choose, good luck.