The application of charitable flying activities such as Angelflight, are narrow. One cannot simply fly a pastor and state that it's therefore a charity flight. Nor can one simply begin transporting medical patients from A to B, regardless of weather one pays the costs one's self, or not. It's just not that simple.
If one is trying to claim deductions for moving scouts, one is trying to obtain compensation for transportation. The issue of transportation is at the heart of the FAA's concern for public safety in these issues, and the regulation surrounding it. Very often, the FAA doesn't get involved or seek any enforcement action until the flight ends up at a point other than the point of departure; until travel or transportation is involved.
A plethora of interpretations exist (how many interpretations, in a plethora?) regarding charity flight, and compensation...and I really dont' want to dredge them up (but we can, if it's crucial). Suffice it to say that the application is narrow, that the FAA assigns operations certificates for a reason, and that commercial certification is required for most all compensation or hire...also for a reason. It's always also well to note that much of our regulation is written in blood. It has evolved as it has not due to political pressures on the word alone, but public scrutiny following fatal accidents. Regulation seldom gets modified or changed but for the deaths of others, that bring the change.