Is it permissible to eat the meat of animals offered as charity by a man to three of Allah's saints—in whom he believes to have the power to benefit and harm—and is it permissible for his children to help him in this?

Whoever believes that the dead or the living can benefit or harm without Allah's permission has committed an act of disbelief (kufr). Praying to the dead or seeking closeness to them through sacrifice and vows is polytheism (shirk). If the intention behind sacrificing for the saints (awliya') is to sacrifice for Allah and donate the meat as charity, dedicating the reward to them, then the meat is permissible and there is no issue with it. However, this does not apply to someone who sacrifices sheep for these saints believing that they can benefit or harm; this is disbelief (kufr), and this act is a means to polytheism (shirk) and a misguidance for the common people. If the intention is to sacrifice sheep and mention the names of the saints over them, then this is major polytheism (shirk akbar) which expels one from the fold of Islam. Sacrificing to other than Allah with the intent of glorification and worship is disbelief (kufr), and whoever does so is cursed. The meat of such a sacrifice is unlawful and impermissible to eat. If the intention behind sacrificing for the saints is to glorify them while mentioning Allah's name at the time of slaughter, then this is major polytheism (shirk akbar) which expels one from the fold of Islam, and such a sacrifice is that of an apostate, the meat of which is not permissible to eat.