@Hotblack 

Hey

While I have not tried this before, I have a feeling this isnt going to work as you planned.. sorry!

In short the routers can likely only be used in normal wifi and not guest mode..  ill try to explain

When guest mode is enabled this stops the clients on the Guest WiFi going out into the LAN (normal wifi), the only place the guests are allowed to go is the internet.     In a normal one router setup, the guest connects to the guest wifi.. his data goes to the router and out to the internet.  In essence it cant "mix" with other traffic on the network.   With this in mind its likely blocked from going out any of the LAN ports, as it would literally have no reason to do so.

This is your issue i believe..

The older routers can enable Guest WiFi, however the only way that data can get to the internet is via a LAN port mixed with the other 'normal' wifi traffic... therefore the LAN port is blocked to guests, therefore it wont work.  Unless this router was directly into the internet connection, its got nowhere to send the guest data.

Guest WiFi would likely work on your main router only, as this can go straight to the internet.   

If you wabt guest wifi all around the house, you are into VLANs (virtual lans) to seperate the guest and normal user traffic.   This is outside the requirements for Home Grade devices, you would need to invest in something like the Omada EAPs to do this.  EAPs are advanced Access Points capable of doing what you requested.

Hope that helps... :)

  @Philbert 

Thanks for your detailed reply Philbert.

If you want guest wifi all around the house, you are into VLANs (virtual lans) to seperate the guest and normal user traffic. 

I think this might be the solution. As it happens I recently replaced an unmanaged switch with a managed Cisco SG200-18 Port Switch. I read that it was a basic model so ideal for people new to managed switches and as it was going cheap, I took the plunge. I've basically got it working almost as an unmanaged switch, IE, I haven't changed a great deal out of the box apart from software updates and inputting basic settings. I didn't read into VLAN's as I didn't think I'd need to for a home network but it seems if i want to separate out the Guest Wifi on my AP's I might have to. 

Thanks again

Edit, I've just had a thought, I suppose I could add a couple of cheap Chinese wifi extenders to extend the Guest Wifi from the main router? 

I've just tried turning off the main Wifi in the AP's and turning on the Guest Wifi to see if having only one Wifi network connecting to the main router would work, it didn't. You can't have Guest Wifi on without the main Wifi being on as well. They aren't making it easy are they!