Is that which an employer grants on religious occasions or otherwise, be it material things or in-kind, forbidden to the honorable descendants of the Prophet (peace be upon him)?

If things are not from Zakat funds, they are not forbidden to the Household of the Prophet (Ahl al-Bayt). Therefore, they are not prohibited from accepting gifts and voluntary charity. Likewise, they are not prohibited from accepting Zakat if their right to the khums (one-fifth) mentioned in the words of Allah the Almighty is withheld: "What Allah has brought as spoils to His Messenger from the people of the towns – it is for Allah and for the Messenger and for [his] near relatives and the orphans, the needy and the wayfarer – so that it will not be a distribution among the rich among you." (Al-Hashr: 7).