Any help would be great
His first movement is to crouch down more to go into knee lift. That’s his body adjusting into a posture in which he has the strength to do what he’s asking his body to do. But that downward crouching movement is wasted movement. You can eliminate it by having him start more crouched down right from the start.
Disclaimer: I am a noob at this.
I noticed that first crouching move too. I think it comes from the kid trying to execute a leg lift. But it’s not right. The emphasis at that point should be on the slight rearward weight shift that accompanies the leg lift, not the mechanical action of lifting the leg itself.
A few other things I don’t like: I prefer to see the arms breaking downwards in a “pendulum swing”, so that the back arm makes a circle downwards before coming to the cocked position. Your son is pulling the ball straight back out of the glove, more like a catcher.
Of course, the glove action is a little loose and wild during the throw; that’s typical for young kids, but it is an area that can be improved upon.
I believe a stride straight towards the batter is a good objective at this age, but I can’t really tell if that’s happening in the video.