Is it permissible to hold a wedding feast by feeding orphans and the needy instead of inviting relatives and friends? Will this bring blessings to the marriage? And is it obligatory to invite relatives and friends to the feast?

The most evil of foods is the wedding feast (walima) to which the rich are invited and the poor are left out. The Sunnah is to invite everyone: relatives, friends, the righteous, and the poor. This brings blessings and prevents discord. Indeed, Ibn Umar used to invite both the rich and the poor. The walima is a meal of gratitude and joy, and it is part of the Sunnah to invite the righteous to it.