At what age should I consider getting my son his own credit card/ a supplementary card?

Not too sure about this. But i feel when i am at that age, i do not have the pain or feel when i spend my parents money. So for me, definitely no.

I would think it's too early and that the minimum is 21. Looking back at myself when I was 16, if I had a credit card i would spend unnecessarily. It would be better to give him a debit card with a fixed amount of $ inside for him to spend. That way he knows that he have this amount and can't spend above, teaching him the importance of prudency. The scary thing about credit cards is that you don't see the real $ spend upfront, only at the end of the the month when the bill comes.

Is he a responsible child? I think it's fine to get him one, but remember to set a reasonable credit limit. This may also be a good way to teach him about responsibility.

Please teach your son budgeting first, but leave him a stash of money as a last resort. A credit card fueled spending spree is the last thing you want.