As someone who has used Newgrounds as a kid, but hardly ever used her ancient NG account to interact (nor do I remember the credentials)... As long as safe for work content is still viewable as a guest, I feel as though that will be enough as is for kids. Waiting until 14 and even up to 16 to actually use this site isn't a bad idea at all. NG's culture/aura is different from other, more popular social medias.
As for the supporter only PM image privilege part... I haven't use NG PMs yet and I prefer talking to people in public spaces, I do appreciate that you can flag PMs as needed, and I'm under the assumption that moderators and admins have access to said PMs, yes? (I'm not sure if someone already mentioned this) I guess this being a supporter perk now would be another reason to financially support NG, but couldn't people use links that would link to images though? I reckon it's nice not to open up a PM of a shock image from a random user.
I'm also fine with the new minor account rule as I don't really use PMs much anyways.
I do worry about the showing ID thing. I trust you guys, but I think my concerns are the same as some of the users.(hackers getting info, data breach, etc.)