You need to speak the victim witness counselor through the prosecutor's office..they work on behalf of victims of crime, that person can help you write up something about how the stabbing affected you and if some one else can read it for you..
He needs to address his issues to his public defender and allow the criminal justice system do it's job...sexual offenses with minor children is a very serious crime..with serious consequences..we must protect our children at all times..
The parent who has the children should then file for full custody of the children if the other parent is in jail..depends on the crime and sentencing..to if the joint custody would be change in court..
When some one take over guardianship of children, the details should be all worked out in front of the judge at the time of the hearing. In order for her to regain her children, she would need to file a motion in court, you should contact the courts for this kind of information, or your lawyer...