One of the main reasons why I put The Basics: Hitting and Throwing together was because, every year, new parents would come into our rec program and make the same mistakes when it comes to hitting.
Lobbing the Ball
The way to do that is to pitch the ball as flat as possible while keeping the velocity manageable. When in doubt, err on the side of a little faster because you absolutely do not want to lob the ball and drop it at a steep angle down onto the plate -- which in the big leagues is called a 12-6 curveball -- as happens when a tall adult stands up straight and just lobs the ball at the plate.
When I am doing coach pitch, I either pitch underhand, from one knee, or while sitting on a short stool or chair. I also throw the ball relatively hard, and much harder than most people do, because I have found from my experience with machine pitch that kids can hit a flatter, faster ball much more easily than they can hit a slow ball that is dropping at a steep angle down onto the plate.
Buying Too Heavy of a Bat
While swinging a heavy bat is good for the ego, it's not good for the swing.
The problem with giving a young hitter a bat that is too heavy and/or long for them is that it can easily create a problem with Bat Drag.