Parental controls for my own devices

[FourOnTheHill]

I have two DC: 7 and 9. Currently they don’t have their own devices but they use mine fairly often. I currently own an iPhone, an old iPhone that they use for audiobooks, two iPads a laptop and an iMac. Most of these I need for work and I don’t want to allocate them permanently to either DC. What I would really like to be able to do is time limit their use so that when I lend them a device and I say they can have it have 30 mins, that it would switch itself off after 30 mins rather than me having to wrestle it off them at that stage. I would also like to be able to stop a device immediately if I suspect someone has snuck off to the bathroom with an iPad. The things I’ve looked at like screen time seem very easy to override and not really suitable when they don’t have their own devices or Apple accounts. I don’t want regular screen limits just ad hoc ones that are quick and easy to programme in. Thanks for any thoughts.