What is the Islamic legal ruling on dealing with a wife who demands the boycott of family and the prevention of children from visiting them as a condition for the continuation of the marriage, threatening divorce if this is not met?

The most effective solution to problems is to apply the Shari'ah of Allah Almighty to them, coupled with patience, wisdom, and self-control. You must mend your relationship with Allah through repentance, by obeying His commands, and by abstaining from His prohibitions. Be firm in upholding justice and establishing equity. Do not allow your family to wrong your wife, nor allow your wife to wrong your family. Make her understand the difference between obeying and honoring parents, and her obedience to you in what is good.