Parents' Rights, Teenagers, and Blood Donation:

I just gave blood today, and thought about how it would be good to one day persuade my kids to do the same. Naturally, this should happen only when they're physically big enough to safely donate, by which time they should be old enough to appreciate what they're doing and why it's good. But I'd like to start as young as possible, given these constraints, since I think it'll be a valuable educational experience, and may encourage good habits and attitudes. And my sense is that, setting aside size and unusual health conditions, such a donation would basically be perfectly safe.

So I wondered: To what extent would I be legally allowed to engage in this sort of parental education? Various Web sites report that many states set a minimum age of 16 or 17, and that strikes me as an unwarranted interference with parents' choices. But my quick look at California law discovered only a provision that specifically allows donation with parental consent at age 15 or older (and without consent at 17 or older), and doesn't specifically prohibit donation at an earlier age. Can anyone point me to laws (in California or elsewhere) that do indeed prohibit donations, even with a parent's consent (possibly with exceptions for emergency targeted donations)? Is there some other reason why blood banks would be reluctant to accept donations from minors who have the parent's consent? Is there some argument that I'm missing for why such donations should be barred?

By the way, I don't think that such prohibitions are unconstitutional (though I suppose that under Pierce and Meyer a decent though not overwhelming case could be made in favor of that position), just that they are -- unless I'm missing some important objection -- improper intrusions into a legitimate parental decision about the child's moral education.