I had a guy approach us in a parking lot and offer my boys a dollar coin. I was kind of weirded out at first but i could tell he was just trying to be nice. He told them he was giving them the coins because they were good boys and helpful to me. He didn't know who we were, but maybe he was just trying to do random acts of kindness.
My first reaction is always to assume people have bad intentions, but I think it is sad not to allow people to be nice to you. I understand trusting your gut, but if you don't feel you are in danger, I don't see the harm in being nice for a minute. You can explain to your children that it might not be safe to keep stuff given to them by strangers. JMO