Are the children entitled to abandon their father because he married a young woman without their knowledge and expelled them?

It is not permissible for children to abandon their father for any reason. Rather, it is obligatory for them to draw near to him, seek his pleasure, and apologize to him, because honoring one's father and accompanying him with kindness is one of the most emphasized duties, regardless of his harshness, as stated in the Noble Qur'an and the honorable Prophetic traditions which affirm showing kindness to parents and avoiding disobeying them. They must take the initiative to reconnect with him and submit to him to attain his pleasure and the pleasure of Allah.