one click shop on Amazon, child settings??

[NewName123]

Have just bought a Kindle Fire for DS. I understand it is linked to Amazon. They will only allow purchase of stuff through this one click thing. However this means that DS can randomly purchase exactly what he wants without me putting a pass word in.
I am trying to alter this but can't seem to manage it. Can anyone help please?

Can you set him up an amazon account that has no credit card linked? Then you but gift vouchers, add them to his account - when they are spent, they are spent.

I think if you go into account settings there are some settings for one-click and you can set a password there.

Set Passwords - parental control, protect purchases.