Is it permissible to hold mourning gatherings where Surat Yasin is recited and the biography of Imam Husayn is mentioned, with the intention of fulfilling needs and facilitating the marriage of a daughter, along with distributing sweets? And is this considered among the permissible acts or innovations (bid‘ah)?

The best guidance is the guidance of Muhammad, peace and blessings be upon him. What is with Allah cannot be attained except through obedience to Him. If you wish to hasten your daughter's marriage, strive in obedience to Allah, in His remembrance, and in supplication, for it is a sharp weapon. As for innovations and superstitions, they neither bring the distant near nor make the close far. Sitting for condolences and reciting the Quran at mourning gatherings is an innovation. Reciting the biography of Al-Hussein is a clear innovation; why then is the biography of the Prophet, peace and blessings be upon him, and his rightly guided Caliphs not recited?! This is from the actions of severe innovators, and we seek refuge with Allah for you from such deeds. We advise you to adhere to the Sunnah (definition), for adhering to it is the cause of attaining every good and repelling every evil.