Greetings wedfasdf,
Screen Time is a great a feature. To confirm, are you using your device to enable Screen Time on their devices? If not, enable Screen Time using the steps outlined there. You can also find these steps outlined in the following article. This would ensure that you're able to manage those settings without having to go in to Settings on their devices.
- "Go to Settings > Screen Time.
- Tap Turn On Screen Time, then tap it again.
- Select This is My [device] or This is My Child's [device]."
Use Screen Time on your iPhone, iPad, or iPod touch - Apple Support
If you're walking through those steps to enable Screen Time for those devices from your iPhone, the next step would be to restart the iPhone. While simple, restarting is a great way to resolve many issues.
- "Press and hold either volume button and the side button until the power-off slider appears.
- Drag the slider, then wait 30 seconds for your device to turn off. If your device is frozen or unresponsive, force restart your device.
- To turn your device back on, press and hold the side button (on the right side of your iPhone) until you see the Apple logo."
Restart your iPhone - Apple Support
Let us know how that goes and we'll continue from there.