Is organizing weddings for Muslims and Christians, while avoiding the serving of prohibited things, considered unlawful (haram)?

This work is a type of ijarah (leasing/hiring), and the benefit derived must be permissible by Sharia. It is not permissible to hire drummers (daffaf) or musical instruments (ma'azif) for weddings, nor is it valid to hire for acts of disobedience. If weddings or conferences include anything forbidden by Sharia, then it is not permissible to organize them, even if the organizers do not directly present the forbidden things.