Is it permissible for divorced spouses to travel together in the company of their children, such as traveling to perform Umrah?

A woman who is revocably divorced and is observing her 'iddah (waiting period) is treated as a wife. Therefore, it is permissible for her husband to be in seclusion with her and to travel with her. As for a woman whose 'iddah has expired, or whose divorce was irrevocable (ba'in), she is a stranger to him. It is not permissible for him to be in seclusion with her, nor to travel with her, and the temptation she poses may be greater than that of a stranger.