Applying for divorce via Muslim law

My friend is married to a girl from Hyderabad and has a 16 month child in their relationship. He is already married to another lady and has 3 children with the first. The reason for his marriage to the hyderabadi was to help a poor girl by providing a means of living. However she was not attracted to her at the time of marriage and even now. They got married in 2013. she was 17 at the age of marraige which my friend only knew at the time of nikah. He was on the assumption that she was 18. Any case the family of the girl and the qazi convinced him to make the nikah. He was not able to make love with the second wife. For her sake he made the child. Now he believe he cannot provide justice to her with the current status. He is not able to love her. So he believes in divorcing her so that she can pursue another husband. Please advice on how to make the divorce so that all the parties (he, his first wife and second wife) are benefitted so that they all can lead a happy life. Today all three are unhappy and stressed. What will happen to the child. Now the wife is more than 20 years old. Please provide the best advice Thanks Abdul Raheem