No. This is not the way.

> give parents the ABILITY to advertise the users age to browsers, apps and everything in between.

Accounts and Applications to services that provide countent are set to a country-specific age rating restrictions (PG, 12+, 18+, whatever). That's it.

None of the things you mentioned have any point to concern themself with the age or age-bracket of the user in front of the device. This can and will be abused. This is very obvious. Think about it.

That is what I meant by age(-rating), you are correct. However, drop country specifics - too complicated. Age brackets are enough: child, preteen, teen, adult. At around 16-17 these should be dropped anyway since at that point people are smart enough to get around these measures anyway and usually have non-parent controlled devices.