الجواب حامدا و مصلیا
In this situation if the wife of the questioner possesses apart from her basic necessities, clothes, equipments and things etc in addition to the referred seven tolas of gold, she will be considered as a Sahib e Nisab (one who has resources) to execute Qurbani, Sadaqa e Fithr etc due to which offering of Qurbani becomes Wajb upon herself as well, and not otherwise. Now if the questioner wishes to offer Qurbani on behalf of his wife it is also permissible, or else, it would remain Wajib on her. She would become a sinner by abandoning it and not the questioner. Therefore it i s necessary for the questioner and his wife to be vigilant in executing Qurbani and Sadaqa e Fithr. However in a situation where the wife is Sahib e Nisab and the questioners is not so then Qurbani does not become Wajib upon him.