Do you have a PayPal account people can send money to, like an email address or a link to donate?
Never, never try and stop people from trying to do good. I would rather be scammed than be complacent.
I'd never knowingly try to stop someone from doing good, but by the same token, warning that this might be a scam is prudent.
Incidentally, when gmail was first released back in 2004(?), Tree dug in and reverse engineered a basic version of it in a couple of weeks. That was before libraries like Prototype were available. His Javascript skills are formidable.