I much prefer the manual batteries for a few reasons. The automatic batteries have a shut off feature that limits the person to a 2-3 second draw. There is a hole in the bottom of the battery of the automatics to sense the intake of breath, liquid can get into this hole and destroy or shorten the life of the battery.
With the manual batteries, pressing the button becomes second nature very, very quickly. Allows control over The length of the draw. with the ego and the 510, long slow, gentle draws work best.
The batteries are sealed, so no liquid can get into the battery.
May also want to look at getting him some drip tips--no filling or refilling carts or cartomizers.
http://www.vaportalk.com/forum/forum/forum/topic/7308-how-to-direct-drip/