brushout,
Thanks for posting. I hope some others will chime in here, as there are many different hitting perspectives voiced on HSBBWEB. Please keep in mind that these comments are all suggestions, and come from a variety of different people. I'd take what you and your son find that works and run with it. Throw away what doesn't. Watch a lot of MLB hitter video. And take criticisms as all constructive!
What I am immediately questioning is if this is your son's "ideal" swing, or if this is your son's "everyday" swing. I would say that the ideal swing may be what your son is trying to do, which he may do via dry swings. However, these mechanics could change a fair amount from dry swings to tee, to soft toss, etc. Just make sure that the swing is correct in each stage.
To know what level we are working on, how old is your son?
To me, it looks like he could use his hips more effectively. In other words, it doesn't look like he has a great hip drive, hip snap, whatever you want to call it. Try to initiate the hip opening by using the back hip to rotate the hips into footplant. Everyone from LL to College guys are learning how to use their hips better. It takes reps to get the right feel. He will know what it feels like. The hip c o c k is important to get the hips started, but someone else who can explain that well can take that part of it. Hips don't have the "counter-rotation" or load that Ted Williams talks about.
Also, the wrists may be "rolling" a bit too early. Wrists should hit like cutting down a tree with an axe. Ideally, wrists are unbroken at point of impact.
Overall, it's a fundamental swing. Baseball is a game of inches. Sometimes minor adjustments can equal huge rewards. Best of luck to you and hopefully others can give you some more constructive feedback.