Can I make sadaqah or give charity on behalf of Imam Hussain? because one hadith say that Sadaqah is not permissible on Prophet and His family.
All praise to Allah Subhan o Taala and blessings on Prophet Muhammad peace be upon him His family and Companions
Narrated Ibn Abbas ra:
That the mother of Saad bin Ubada the brother of Bani Saida died in Saad's absence, so he came to the Prophet saying, "O Allah's Messenger (ﷺ)! My mother died in my absence, will it benefit her if I give in charity on her behalf?" The Prophet (ﷺ) said, "Yes." Sa`d said, "I take you as my witness that I give my garden Al-Makhraf in charity on her behalf."(Bukhari)
Narated By Abu Huraira : Dates used to be brought to Allah's Apostle immediately after being plucked. Different persons would bring their dates till a big heap collected (in front of the Prophet). Once Al-Hasan and Al-Husain were playing with these dates. One of them took a date and put it in his mouth. Allah's Apostle looked at him and took it out from his mouth and said, "Don't you know that Muhammad's offspring do not eat what is given in charity?"
You could give sadqah or charity on behalf of beloved of Prophet Muhammad peace be upon him Imam Hussain ra and the Hadith which you have mentioned says that Charity is not to be taken by Prophet Muhammad peace be upon him and His family so not to get confused by that giving away charity to others were not permissible for them and he always gave any excess in wealth to charity (if he had any),so it is pemissible to give on behalf of Imam Hussain ra.
Allah swt and His Messenger knows best.