While in the state of ihram, may women keep their faces covered (wear the niqab) and wear gloves (kuffazayn)?

No. In this state, she should not wear a niqab or gloves. However, if a non-mahram man comes into her presence, she should keep her face covered. That is, she is permitted to cover her face with a headscarf or another piece of cloth, without wearing a niqab.