Thanks for the hint. I was just about to buy an old compact camera for my daughter as she sees me taking pictures with my sony a7. Maybe you are right compact cameras are awful usability.
What software did you use to lock it down? I have some older iPhones laying around.
The iOS built-in Parental Controls settings can be used to enable/disable access on an app-by-app basis; that's probably all that's needed here, since Camera + Photos by themselves don't give you any built-in web browsers. (Camera.app can scan QR codes, but it just pops a new tab in Safari when you click them, and Parental Controls would block that.)
In contrast, my daughter sees us use our phones and uses them as well. I simply uninstalled all the apps I could and used the Google Family link stuff to lock it down further.
You can get really creative with an Android phone. Install LineageOS with only the minimum gapps you want. Lock down everything, remove the play store, add Tasker to make the UI black&white when using apps other than photos/camera install a launcher like nova to further customize what apps are visible/easily accessible. You can even completely remove Chrome but still install the web browser component so things like your e-mail app work but you can't easily browse the web.
I did this for a while a couple years back to discourage myself from spending so much time on my phone. Worked great and I would have kept it up if it were not for my wife constantly complaining that I couldn't look anything up or use Yelp or Messenger or... :D
What software did you use to lock it down? I have some older iPhones laying around.