I think you are taking the initiative, which is great, and taking the advice given before, would definitely improve your photography.
As off being off in the distance, a great deal of photography involves talking to people,directing and letting people know your vision, so I'd say approach these guys and simply ask if you can do some pics, maybe tell them you'll give them the cool ones afterward, and I'm sure they;ll play ball, and let you get closer.
Just watch out for your glass though, you never know were the skateboards are going to go when they miss a trick.