When my sons goes to play a cover drive the ball tends to go to mid off. Is it his feet, hands or is he trying to hit the ball too hard. How can I help him?

Tim, it could be all of those things, but ultimately it comes back to aligning his leading shoulder, elbow, knee and foot to the direction that he wants to place the ball. It is also crucial to wait for the contact point to be under his eyeline, which should also be over his from foot, and not reaching out in front, as that normally pushes your bottom hand through, and the bat would be moving back towards the mid off position, thus, not presenting the full face of the bat towards the cover position.
Batting tee drills are excellent to get all of these elements working together, rather than bowling machines or throw downs. Set up one on the driving length, and two in the target area (cover). Make sure that it is about the contact point and keeping your elbow up and moving through the target zone, and that his toes are pointing through the target zone as well. To time cover drives you do not need to have a massive follow through, so strike it and bring your elbow up to eyeline height. Remember, when doing drills you should have your normal equipment on to ensure that the position you achieve in practice , can be replicated in a match.

Hi Tim...

I love this question... batting is a head-and-hands game.

A couple of comments...
1. Not personally big into the high elbow theory as a focus point. The grip of the bat will determine where the elbow goes.)
2. I don't think there is something like trying to hit the ball too hard. More a matter of strength and skill not well refined yet. When hitting a ball, we need bat speed and the ability to keep our bodies in a stable, balanced, strong position.
3. Not fond of hitting balls of batting tees as I have seen more than enough times players hit them great off tees only to still not do it with a moving ball.

It would be interesting to see a video of what this problem looks like as a more accurate assessment can be made then.

How I would go about it...
Throw the ball with two bounces outside off stump and ask your son to hit the ball through mid-off, then extra cover, then cover, then point. First, do this in order... then vary the targets. Most importantly ask him to fee the difference in hitting the ball to the different targets.

Once he can do this go to one bounce and then faster throws.