Your child doesn't need an email address or a password. Instead, your family gets one shareable link, and each child gets their own short PIN. Together, that's enough for your child to sign in on their own - to a screen that shows only their topics, with no menus, settings or billing anywhere on it.
Set it up
Go to Kids' login (linked from your dashboard). There you'll:
Choose your family's link - a short, shareable web address unique to your family. One link works for every child in your family; each child picks their own name on the next screen.
Set a PIN for each child - 4 to 6 digits, chosen by you. The PIN is shown to you exactly once, at the moment you set it, and never again - so this is also the moment you'll be offered a printable sign-in card with the link, a QR code, and your child's PIN, sized to stick on a fridge.
Repeat for every child who should be able to sign in themselves.
How your child signs in
Your child opens the family link (by typing it, scanning the QR code, or opening the shortcut/app you install for them), picks their own name and picture from the family's list, and enters their PIN. That's it - no navbar, no account, nothing but their own learning.
Losing the PIN, or a lost device
If you've lost the printed card, open Kids' login and select View card on that child's row - it reprints the same link and QR code (the PIN itself can't be shown again). If you need to change the PIN, or a device needs to be signed out (lost, sold, or just returned after daycare), the same screen lists every signed-in device and lets you sign one out, or sign out everywhere at once.