Are elderly parents excused if Allah takes their souls while they hold unsound Islamic beliefs and concepts – derived from Sufi orders and sheikhs who do not deserve the title – due to the current unavailability of a sound source of information for them?

Knowledge is religion, and it must only be taken from its rightful people. Therefore, it is not permissible to imitate innovators (Mubtadi'ah) and people of whims (Ahl al-Ahwa'), because they may distort the truth. Sufism is based on corrupt ideas, and taking knowledge from someone who follows these ideas is very dangerous, especially for the common people. Strive to guide your parents through supplication and guidance. Whoever's Islam has been established with certainty, it cannot be removed except by a similar certainty. The doubt may strengthen for some due to their trust in shaykhs whom they believe are teaching them the correct religion.