Wa alaykum assalam wa rahmatullah wa barakatuh

 

In the Name of Allah, the All-Merciful, the Mercy-Giving

 

All praise is due to Allah. Peace and blessings be upon His Messenger Muhammad.

 

As long as the work you will volunteer to do is permissible, you may do it, even if it is run by non-Muslims.

 

In fact, being a volunteer gives you more freedom to abstain from doing whatever you may have doubt about. A Muslim may- even should- help others to kindness and charitable deeds as the gracious Quran enjoins, “You shall help one another to virtuousness, and to the fear of God. But you shall not help one another to sin and to aggression.” (Al-Ma’idah 5:2)

 

Almighty Allah knows best.