Allow me to offer my insight to the situation. You see, I used to DO this when i was younger, not too long ago.
If I had to guess, I would say the kids hiding behind the car were involved. Them being little kids, of course they want to stick and see what happens when they pull such a prank. The ones running away could have been part of the same group but just had the sense to get out of there. Even if they werent a part of it I would feel pretty certain they knew who it was. After all, its not cool to “rat out” your friends.
Going to their parents could have mixed results. Be prepared for the possibility that the parent doesnt care that their child is doing this. I know one of my friend’s parents didnt care.
My recommendations? Have you thought about installing a motion light? I know from experience that it takes a lot of balls to “ring and run” a house with a fully lit up porch.
Other than that, just stop answering the doorbell. They keep doing it because its funny and entertaining. Make it boring and eventless and they are sure to stop. I know it might be irritating at first, but do you think after, say, 15 nights (that may be a little excessive :P) of not getting a response that they are going to keep ringing it?
If all else fails, scare the sh*t out of them. Doesnt have to be anything elaborate. I know one house we stopped going to because after we rang the doorbell one time we hid in a small patch of woods beside the house. Well, the owner came out and proceeded to creep toward us very slowly. (How he saw us I dont know) But he got right up on us and right before he got close enough to grab us we bolted in two different directions, hoping we wouldnt get caught. Well that was a little too close for comfort, and like I said, after that we never went back.