Mark, here is a what I posted about kids bows back in November on the "All power tool bow challenge? " thread:
lowell, that bow as made for a six year old. If you make a bow's weight about equal to the child's age (girls), you're pretty safe. What I mean by that is the bow will not be too strong for the child and the arrows will not fly with too much force (in case of an accident). After age twelve, a child's strength starts to increase dramatically, so I add 5 pounds to the draw weight. After age 15, I add 10 pounds to the draw weight. So....for example:
Age 5 = 5# bow
Age 12 = 12# bow
Age 13 = 18# bow
Age 16 = 26# bow
These examples are for girls, using my daughters as a guide. My boys are only 5 (twins) and I'm sure they will be a bit stronger than the girls, but for now the chart above works well for them too.
As far as draw length, just add their age + 10 to determine the number of inches. Examples: a 5 year old can pull 15" and an 18 year old should be able to handle 28".