want to buy some shares for my 12 year old son, page-14

afi
arg
mir [might be best choice because he's young and can adopt a riskier approach- not that MIR is particularly risky]

However, You need to be aware of children's tax- he will pay 65% on returns over ~$650- not sure of the exact figures but they make it prohibitive for a child to have any investments which make unearned income. I'm pretty sure this includes a bank savings account.
Solution is a share-based insurance bond which is tax free after around ten years. [again, i'm a bit fuzzy on the detail, DYOR]