If you want to give someone the ability to turn a specific set of devices on and off and nothing else, most people use one of the paid third-party dashboards like action tiles or SharpTools. They are perfect for that use as the person will have no ability to get any other parts of your set up. ( The action tiles license fee is per hub, not per device, so you would also be able to use it to set up custom tablets or other phones if you wanted.)
I’m tired today, but there are multiple threads in the forum discussing these options. I believe Both have a free trial If you want to check them out.
These run in any web browser, so you can use them on most phones.