Sending hearbeats from WDS repeaters

I have the following setup:
One central AP connected to the internet, several WDS repeaters connected to the central AP, some connected to other WDS repeaters (multiple hops to the central AP). Only the cnetral AP runs Coovchilli. So when a customer connects to a WDS repeater, the splash screen comes up to allow for authentication through coova. So far so good.

The central AP runs a heartbeat - vai cron it calls a website on my server every few minutes.

Here is my issue:
I would like to receive a heartbeat to monitor all my routers, including the WDS linked ones, but since they are not authenticated themselves to coova, they cannot ping the internet. Only clients linked through the repeater to coovachilli and successfully logged in, can see the internet.

What can I do for the WDS routers to bypass coova authentication on the central AP and send a heartbeat, but still enforce the normal splash screen and authentication to all devices linked to WDS router?

All input welcome.