I know it isn’t the best quality, but just would like to see how he is doing?
I like what I see from your son. He has a good number of movement going on here in his delivery. Nice job. One of the movements that stuck out to me that can be worked on in time is lack of forward trunk tilt at ball release. I realize he is only 9 so the most important suggestion I can make to you is to continue to keep baseball fun for him. You can always work in some drills that will eventually help him with forward trunk tilt at ball release.
Lack of good forward trunk tilt can become an issue for a couple of reasons. First, it reduces velocity both real and perceived. Right after front foot plant, you want to be bracing up with your front leg so that you can catapult powerfully over your front leg with your chest and throwing arm. By finishing too upright, you lose some of that catapult effect. Good trunk tilt also gets you out farther over your front foot allowing you to release the ball closer to home plate and increase perceived velocity. Ideally you want your head and chest over your front leg with the ball leaving your fingers at or past your front foot.
If you have any questions feel free to ask
Steve - EBP