Is it obligatory to tell children about their parents' divorce and the father's remarriage, or is that not the new wife's concern and she should focus on her relationship with her husband?

It is recommended to have witnesses for divorce to safeguard rights and prevent disputes, based on the Almighty's saying: "So when they have fulfilled their term, then either retain them in kindness or separate from them in kindness. And bring to witness two just men from among you." Some of the Salaf interpreted this as bearing witness to both divorce and reconciliation. This witnessing is not a condition for the occurrence of divorce, by scholarly consensus; divorce takes place even if it is not witnessed. The husband is not obligated to inform anyone of his wife's divorce, but it is advised to document it officially to safeguard rights. It is not permissible to conceal a divorce if it results in the divorced woman remaining in her former husband's house after the expiry of her 'iddah (waiting period), because she then becomes a stranger to him. The divorced wife must inform her guardian of her divorce, and no one has the right to force her into marriage if she does not wish to.