The issue here has absolutely nothing to do with how it affects kids, it has to do with how it affects adults. Again: "States are basically requiring identification to speak or criticize government in the town square."
The fact that the legislation is intended to affect kids is irrelevant if the only legally permitted way to comply damages the individual liberties of adults.
To be clear, I'm not trying to suggest an ulterior motive on the part of DeSantis or the Florida legislature. But effectively requiring a government ID to exercise free speech on the internet damages individual liberty (again, of adults) regardless of whether that's an intended effect or not.
The fact that the legislation is intended to affect kids is irrelevant if the only legally permitted way to comply damages the individual liberties of adults.