What is the ruling on women mixing with men at the grandfather's house, and is it permissible for the wife to go with her husband and remain in full Islamic hijab, or must going be avoided altogether?

The mixing of men and women is forbidden due to the corrupting influences that result from it. It is not permissible for a woman to remove her hijab in front of her husband's brothers, their sons, or his paternal uncles, because they are not her mahram; rather, they are non-mahram men. If the wife goes to her husband's family home and finds there someone in front of whom she cannot uncover, she must remain in her hijab. There is no harm in her sitting with the family if the prohibitions of looking, khalwa (private seclusion), shaking hands, and softening the speech are absent. It is preferable that she have a separate sitting area with the women so that she can remove her hijab and speak freely. As for being lenient in mixed sittings, conversation, laughter, handshakes, and looking, this is forbidden.