Time controlled security for my Wifi

Hi,

has anyone of you a good idea how I can comfortably set up a schedule- driven wifi access for my kids ?

I am using an Asus RT- N66U and configured a 2.4 and a 5 GHz network. Unfortunately, the built-in child safety lock seems to have reliability problems.

I have now converted the 2.4 GHz network to WPA2-Enterprise and built a small RADIUS server on a Raspberry Pi. It controls different users with individual login times. This works great, but:
While most of the devices (laptops , smartphones, tablets) run as desired, unfortunately there are a few devices that refuse to connect to a WPA2- Enterprise. So far I have noticed
- Google Chromecast
- Amazon Kindle
To switch the 5 GHz network over to WPA2-Enterprise and to re-establish WPA2-Personal for the 2.4 GHz network would not work, as one of my two kids owns a smartphone that only works on 2.4 GHz. And maybe this is not the only device.
A third Wifi network (2.4 GHz with WPA2-Personal for the devices mentioned above) sounds a bit exaggerated for a 4 person household, right?

I tried to find alternatives for the RADIUS server solution but could not find any time controlled services (like DHCP) within the network/security chain.

Can anyone give me hint?

Wolfgang