My youngest son, now 11 has a Diamond that I got for him 3-4 years ago from a friend whose son outgrew it. It has been a great bow for him after transitioning off of the little Bear fiberglass bow he had before. Should continue to be a good bow for him for a couple of more years until his frame justifies a bigger bow.
Like your buddy mentioned, weight is very important at that age. Every ounce that they do not have to hold out in front of them at that age is huge! My youngest picked up the Diamond and had no trouble holding and shooting it at all.
I bought my older son (14) a Hoyt (which model escapes me at the moment) when he was 6-7. It is a superior bow by all measure, but is much heavier in the hand than the Diamond. Plus it was double the cost.
My oldest got the Viking gene from me and was a much bigger kid than my younger son at the same age. That said the Hoyt was still very difficult to shoot for him when he was young because of its weight and the small amount of draw weight that he could haul back.
On the other side of that coin though, he is now 14, 6'-1" 170lbs and still shooting the same bow at 28" and 65lbs of draw weight. This bow could literally be shot until he is out of high school and is done growing.
IMO, I would buy the larger possibly better bow if he is a big kid. If he is smaller like my youngest, the Diamond is a great choice.
Either way, you cannot go wrong. The important thing is that you are passing along the tradition!
Another word of advice.......
Enjoy out shooting your kid while you can, for it will not last long!
