I also would like this. Best I have seen is another post from someone who created a second instance of Hassio and passed on only the devices they wanted via an add on for their kids accounts.
The authorization system in HA is fairly basic so far. So much that you can’t really prevent other users from accessing any entity. wolfhunter1043 suggestion is the best I can think of.
Personally I don’t use HA for cameras, but have a dedicated server for that with a robust permission system.