My recommendation would be setting up Nobara with a separate home partition so you can easily switch if it stops being supported, although there are no sign of this yet. My second recommendation would be Opensuse Leap, it is more stable and well established but less optimized for gaming. Maybe take another look at Pop OS! when they release their independent new desktop. If you go with base Fedora be aware setting up codecs can be annoying. Avoid Manjaro, the distro breaks a lot due to dependency conflicts. Also I think you mean GNOME 40, GNOME 3 is the old design.
Parental controls are one of the under developed parts of Linux, the only major one I know of is timekpr