Possible answers to child safety?

In Reno vs. ACLU, the court decides the anti-indecency sections of the Communications Decency Act to be unconstitutional because of the following:

"We, [the court] are persuaded that the CDA lacks the precision that the First Amendment requires when a statute regulates the content of speech. In order to deny minors access to potentially harmful speech, the CDA effectively suppresses a large amount of speech that adults have a constitutional right to receive and to address to one another. That burden on adult speech is unacceptable if less restrictive alternatives would be at least as effective in achieving the legitimate purpose that the statute was enacted to serve."

Is it be possible for ISP servers to make it mandatory for children and adults enter a password before gaining access to the Internet? If so, there could be a "filtered" internet that only children have access to. If they wanted to gain access to an "un-filtered" internet with adult content, they would have to gain consent from their parents first. By the court's definition, would the password accessible Internet for adults and children be considered a "burden" on adult speech?

Also, this "password accessible internet" would be useful in preventing child predators from connecting with children. ISP's could require registered sexual offenders to have a different password to gain internet access. Then, their internet access would prevent them from entering children chat rooms.