Is it permissible for a niqab-wearing woman to go to wedding halls to offer congratulations and then leave immediately, while being careful not to participate in the rituals of the place and to avoid displeasing her family?

If your attendance at weddings is outside the times of forbidden acts, or you do not witness forbidden acts there, then it is permissible. However, your attendance at times when forbidden acts occur and are seen is not permissible, unless you are able to change them. Otherwise, it is not permissible to attend, even if relatives are displeased. The reason for abstention should be explained. For the Messenger of Allah, peace and blessings be upon him, said: "Whoever seeks Allah's pleasure by the displeasure of people, Allah will suffice him against the burden of people. And whoever seeks people's pleasure by the displeasure of Allah, Allah will entrust him to the people."