Is it permissible for children to retract their waiver of their share of inheritance to their male siblings, especially if the waiver was made at the mother's request and out of shyness, and what are the consequences of that?

The two houses your father left are a right for his heirs, both male and female, based on the Almighty's saying: "For men is a share of what the parents and close relatives leave, and for women is a share of what the parents and close relatives leave, be it little or much - an obligatory share." The claim that the children of females do not compete with males for inheritance is closer to the claims of Jahiliyyah (pre-Islamic ignorance). If the daughters relinquish their right out of shyness, this relinquishment is not valid, based on the hadith: "The wealth of a Muslim person is not lawful [for another] except with his willing consent." And that which is given under the sword of shyness is not given with the willing consent of its owner. The daughters are not obligated to obey their mother in this request, but they should politely refuse and express their need for their share of the inheritance.