Is it permissible to change the intention of dedicating a mosque from being solely in memory of the mother to being in memory of both parents? And is such a revised intention accepted in Islamic law?

It appears that the father of this person does not benefit from the endowment because all its reward went to the mother. If the intention of seeking proximity [to Allah] for the deceased was stipulated before the act, then the father was not intended for it. And even if the gifting of the reward after the act is permissible, the entire reward was already gifted to the mother, and it is not permissible to include anyone else with her subsequently, because that is considered a retraction of the gift, which is not permissible.