Ray is just the sort of man who'd be haunted by this sort of crime, especially with his love of and desire for children of his own, to know someone had them nad then abused them, killed them; it'd be too much for him to sit back and not confront the man who killed them, regardless of age/mental health.
One tiny nitpick though, when Ray went to see him the doctor says the statute of limitations on the murder of his children would have passed. There is no statute of limitations on murder.he may not have been re-charged of anything given that he's already incarcertaed but it'd probably ensure he was never released or moved to a less secure facility.