You didn't specify anything about evidence on the car. For now, I'm going to say that means there is none, except maybe some blood on the tires.
I would gather the boy up and drive him to the hospital, then say that I found the two of them in the middle of the road - someone ELSE had hit them - and that the blood on my tires was from when I drove through.
In the case there IS other evidence, the police wouldn't be investigating my car for another couple hours in any given situation, except MAYBE the case of the boy being somebody important's child. That's more than enough time to eliminate any blood, skin, or hair that may happen to be on the car.
Simply put, just because you take the kid to the hospital doesn't mean you'd automatically be suspected of being the one that hit them. Realistically, you wouldn't be suspected for a while.
SW-5120-1900-6153
