Is it permissible to change the newborn's name from "Mahmoud" to "Ahmad" after it had been agreed upon with the husband, due to the desire of the wife and daughters, knowing that the husband wishes for the name "Mahmoud" and everyone calls them "Dar Abi Mahmoud" (House of Abu Mahmoud)?

There is no religious impediment to changing the newborn's name before it is officially registered on the seventh day, especially if the name was merely a suggestion. The names "Ahmad" and "Mahmoud" are both permissible and praiseworthy because they are among the names of the Prophet, peace and blessings be upon him.