Take a look at this V-brake Adjustment Guide Video
To adjust the reach of the brake (bring the lever closer for those little hands), all you need is a 2mm Allen (Hex) key.
The reach adjustment screw is a set screw located inside the brake lever. You can find it by looking at the handlebar from the side. To decrease the distance between the brake lever and the handlebar turn the reach adjustment screw counter-clockwise.