-the way you're holding your pick... I can see (and hear!) that you're holding your pick so that you have way too much of the pick hitting the strings... this produces a "slappy" sound that you can hear pretty distinctly. Try to choke up on the pick so that you've got just a little bit sticking out between your finger and thumb... once you get the idea, you'll really like holding this way, and you'll find you don't drop your pick very often, if at all.
-if you're going to teach something (and I think you can do a really good job) pay attention to details... really listen to the music, and listen to what you are playing, and see where you can improve your accuracy so that its closer to the original. People will really appreciate it if you can make it as close to the original as possible. So in this case, you're just letting the chords ring out... listen to the actual song... hear the difference? He's "stopping" the chord from continuing to ring out by simply muting with the palm of his picking hand... so instead of "dadada annnng annnng annng..." as the chord rings, its "da-da-da (silence)" "da-da-da" (silence)" "da-da-da da-da-da da da-da" etc... (http://www.youtube.com/watch?v=N_5kv8QeBBc)
The stop/mute technique is a big part of Young's sound & style, so don't miss it.
Its great that you're doing awesome at such a young age... I think if you worked on it a bit more, you could get it down pretty easily, and then do the video again and really inspire other young players.
Please don't get upset that I'm giving you some criticism, I mean it as a total show of respect, that even though you're young, I'm not going to condescend to you... you're making a great start... now see if you can get the intro pretty much like how Young plays it... I think you can do it!