All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.
It is not permissible for your daughters to help their mother in being disobedient and cooperate with her in this regard, as this is helping her in sin. However, this does not wave their right of spending on them. Rather, you are obliged to spend on them unless they get married or have enough money that suffices them and do not need your help. Nonetheless, they are obliged to be kind and dutiful to you and keep ties with you.
You should solve this matter with wisdom and in a soft and good manner, and try to reconcile with your wife and not accept to divorce her or grant her Khul’ unless there is no other alternative than separation.
It is permissible for you to accept Khul’ and you will be obliged to accept it if the Islamic institutions order you to do so. Some scholars, like Al-‘Adawi from the Maaliki School of jurisprudence, stated that a just Muslim community substitutes the judge in every matter in which it is impossible to reach the judge or when the judge is unjust.
There is no need to compare the state of the nation nowadays with the state that our righteous predecessors were upon.
As regards the fear that your daughters may believe that a wife may freely separate from her husband, then you are right to think this way. However, you should know that the fact that divorce is in the hands of the husband, does not mean that he is permitted to be unjust to his wife or harm her. Otherwise, she may resort to the court in order to remove injustice and harm off her.
In any case, the best solution is to try and reconcile with your first wife in order to reunite the family especially that you mentioned that she is a good wife. Therefore, you should try to please her by speaking good words to her or doing a good act towards her, and you should not resort to divorce or to Khul’ unless this is the last solution.
For more benefit, please refer to Fatwa 81469 about the ruling on polygyny, Fatwa 90132 about the ruling on how a woman can overcome her emotions and jealousy, and Fataawa 88233 and 84687 about the ruling on the obligation of spending on one’s children.
Allaah Knows best.