That legislation should be coupled with the removal of legal liability for children by parents. It cuts both ways, if parents are unable to make choices for their children (even if they are wrong choices) then they should be absolved of all legal responsibility for said children as they are no longer able to act as the guardian in a manner that they view as the best course of action by their children. I would go further and say all financial responsibility as well. Either we are a society that entrust parents to raise their children or we let the state raise them.

What you propose is legislating the greater body for the unsavory actions of a minority while it is becoming more common with more and more federalization of law it always conflicts with personal freedoms and leads to a less free society for all. Someone would find an action that you do at some point in your life, unsavory and illogical and quite possibly harmful to yourself or others, under what you propose we could just enact legislation for the greater good. This runs contrary to the spirit of the law of the land and ends up somewhere closer to fascism. Please note I am not implying that you are advocating fascism but taking away peoples choice to self determination even for their children certainly starts to lay the foundation for a very different society.

What you propose is a slippery slope on the path to the state raising children which in my opinion is a far scarier reality. Life involves risk, and sometimes it involves risk for children. I think it is fair to say if one has made a life choice that puts other kids at risk their kid cannot participate in activities that could place other kids at risk but it is a whole different level to mandate that we start making medical decisions for parents. If we do we should legally acknowledge that parents or at least the legal concept of guardianship as we know it no longer exist.