The biggest reason why your son has has probably lost his teeth is due to dental decay (caries). When some peoples teeth develop they do not mineralise enough i.e. have a calcium defiency this means the enamel (the outer layer) is not as strong or protective. The main reason for dental decay is plaque build up. Breast feeding is important to pass the mothers immune system (antibodies) on to her child.

There are great ways to replace your sons teeth the best being dental implants which as you rightly state is reliant on the jaw bone. It is estimated that bone deteriates at approx mm per year when there is no tooth present. we can now do wonderful things to regenerate bone so all hope is certainly not lost.
I hope this helps you.