That would do, for direct sales to minors, but I believe most sales would be through a parent anyway, which could get around the system. Would you start having to screen the ones you're verifying?
I believe it could be done, but with screening you're also finding other problems... Though I'm not sure any good parent would lie if you ask them if they plan to give the gun to a minor. Though, it's the good parents that have the responsible kids, it's the bad parents that have the irresponsible kids.
May have to go through a screening of irresponsible 18+ then too.
Though, that would stop direct sales, when the parent isn't involved. That would be a good thing, seeing those kids were most likely to do something stupid with it.
That's my opinion...