Is there any Sharia impediment to holding or organizing parties and events such as weddings, graduation ceremonies, birthday parties, and conferences, provided that only sweets and decorations are offered, and music, alcohol, and forbidden things are avoided?

It is not permissible to rent out halls to those who would rent them for committing unlawful acts. It is not enough to provide lawful services to clients; rather, it is obligatory to prevent access to those who would rent them for unlawful purposes.

If the occasion is permissible, there is no harm in providing services for it, even if it includes something objectionable, provided that the service provider does not attend the objectionable act. However, if the occasion is unlawful, such as birthday celebrations, then providing services at that time is considered cooperation in sin.