When someone gives you money to do your charity work, they deserve to know their money was well spent and bought what you said it would.  Not that you would squander their donation.  It’s just that you ought to tell them.  (They might give a follow-up donation for future projects.)

I was talking to someone from a church I helped for a while about a decade ago.  They needed a new sanctuary, and a partner association wanted space for volunteers to stay in when they came to help.