Should I visit my paternal aunts in compliance with my father's dying wish, or is it not obligatory to visit them due to the problems that occurred and caused my father's death?

Kinship ties are obligatory, and paternal aunts are among the kin whose ties must be maintained. This is further emphasized by your father's recommendation concerning them. Your mother must not be obeyed in her command to sever ties with them, as it is a command to commit an act of disobedience, and there is no obedience to a creature in defiance of the Creator. Your mother must be convinced, and the ruling of the Sharia must be explained to her. Maintaining kinship ties should be done in a proper manner, the minimum of which is refraining from boycotting, returning greetings, and inquiring about their well-being. Your mother must not be obeyed if she commands you to sever this minimum level of ties. Anything beyond that is supererogatory, and your mother may be obeyed in severing it, because obeying her is obligatory, and an obligation takes precedence over a supererogatory act.