Is it permissible to perform Umrah on behalf of a sick, incapacitated grandmother out of love for her, and on behalf of a deceased grandfather who did not pray? And is it permissible for a woman in ihram to use some good-smelling products?

It is permissible to perform 'Umrah on behalf of an incapacitated grandmother. The more cautious approach is for you to enter into the state of ihram on her behalf from the miqat of your country, even though some scholars have permitted entering ihram from Al-Tan'im. As for using cream, shampoo, and scented pads during ihram, if the scent is not from the intended perfume, then there is no harm; otherwise, it must be avoided.