Based on Ed-too-many-letters, I got my son a Samick Sage Takedown when he was 7 or 8. It's a 25LB, and now that he is 10, he can draw little bit better. I don't know much about bows, (what I learnt through this purchase) but the advantage of the Samick is that over time you can replace the limbs for longer/stronger ones, as long as the riser fits the hand size. BTW my younger kids (9, 6, 4) still have some trouble with the draw weight.
I agree with an archery shop trip. Ed had seen and taught my son how to shoot when he made the recommendation, so it wasn't a blind rec.