Obviously the most important thing is that they have fun, if a kid loves hockey it can be a fantastic part of his life, something he sticks with till he's an old man and a great way to stay in shape, build friendships, get the competitive spirit flowing, learn toughness and sacrifice and effort, etc. But push him overly hard and he might end up resenting/hating the sport, and get very little out of it.
If your kid is very motivated, loves the sport, and eager to improve, I'd mostly have him work on his skating. I'm not saying neglect everything else, but the guys who are great skaters when they're young become great players for life. Shot, hands, positioning, etc., all of these things are easier to pick up when older, but it really helps to have skating nailed down when younger, rarely do you see a guy who is great with the puck but a poor skater at 14 become a great skater by 18, but plenty of speed demons who are weak with the puck at 14 become great all around players by 18. And what I mean by great skating is mostly great edge control:
- Kids should be able to turn hard with lots of weight on their inside edge/skate (too many guys just use the outside skate with their inside skate basically tagging along for the ride, a real sign of poor edge control/balance, you turn harder and more effectively with both edges engaged). Being a fast, balanced, instinctive skater in game situations is all about being totally comfortable using both edges of both skates
- Perform hard 2 footed stops in both directions (again, this is really all edge control)
- Maintaining a good athletic stance at all times (knees/ankles bent, head up, feet shoulder width apart or wider if contact is coming)
- Quick acceleration with toe starts from a stop/out of a turn
- Strong crossovers in both directions, going backwards and forwards
- A powerful full-speed forward stride, with fairly full extension, toe flick, and rapid return to the neutral position right after the push
- Learning to maintain speed in a variety of situations
Or just read the Cole's notes version