What will happen if he and his wife file a uncontested no minor children divorce but they have children in common?

Yes they would be in trouble, that would be fraud upon the court. At the final hearing one issue that must be testified to under oath is whether they have any minor children of the relationship. If they testify falsely they would be committing perjury, fraud on the court, and could be held in contempt by the judge. As such the only course of action is to include the children in the divorce pleadings, do the parenting plan, calculate child support and follow the law.