A woman uncovering her face in front of her stepsons
Is it permissible for my mother to uncover her face in front of her stepsons and shake hands with them?
There is no problem if your mother reveals her face in front of her stepsons from another wife, as they are considered as Mahrams (spouse or permanently unmarriageable relative) to her. When mentioning Mahrams, Allah (Exalted be He) says:
...or their husband’s sons
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family, and Companions.