On the one hand is the evil of failing to do whatever it is you needed the car for. On the other is the evil of theft. The difference between the two cases is that the former evil is trivial (e.g. you can't spend as much time with the family because you have to ride the bus) in the first case and severe (e.g. you can't protect your family's lives) in the second case.
Or, alternatively, you are contemplating the means of grand theft auto to achieve the end of being able to drive home from the office (first case) or to achieve the end of saving the lives of your family (the second case).
Again, a distinction without a difference.
(And, even if we stipulate that there is a difference, you have utterly failed to respond to the arguments raised by people who have actually read the HP books that the protagonist is, in fact, correctly choosing the lesser of two evils when he finds it necessary to do so.)
In the first case, the father commits an evil (car theft) to bring about a good (a car for his needy family). The correct moral decision is not to steal the car because the first principle of morality is to do good and avoid evil.
In the second case, the father has a choice between doing nothing and risking the lives of his family or stealing a car. Both acts are intrinsically evil, but car theft is the lesser evil. The father would be absolved of moral culpability for choosing the lesser evil.
In every case in the Potter books is Harry choosing the lesser evil, or doing evil so that good may come? Somehow I doubt that it's always the former.
Regardless, this is a tangential objection to the series. The central objection is that the protagonist is a practicing wizard/warlock.
Have you answered my question yet about whether a person should be allowed by the State to sell himself into slavery, or hire someone to kill him?