If I wear the niqab considering it to be supererogatory, is it permissible for me to uncover my face in front of non-mahram relatives?

Scholars differ on the ruling concerning the niqab, and the more preponderant opinion is that it is obligatory, especially when there is a fear of fitna (temptation/strife). However, the difference of opinion is considerable, so there is no blame upon one who, through ijtihad, believes it is not obligatory, or follows those who hold that opinion. Nevertheless, it is preferable not to uncover the face when visiting non-mahram relatives, because "the in-law is death."