I once donated a flight in my Bonanza for a charity auction.
After thinking about it, I didn't like the possibility of a 300+ pound person grabbing the door as a hand hold while getting in, bending it, making the airplane unairworthy.
Or a passenger getting airsick and making a stinky mess inside the airplane.
Or several other possible negative outcomes.
I attended the auction, and bid on my own flight. The charity still got the donation, and no worries about a non-aviator not knowing how to act around airplanes.
I've decided that if I'm asked again to donate a flight, I will pay my local FBO their going rate for a charter sightseeing flight.
They have instructor pilots used to dealing with passengers unfamiliar with airplanes..