Sonoff 4 ch pro integration with (european) 3 buttons + relay light

Hello every one, first post ever on this amazing forum.

Total newbie.

This is the idea: integrating a sonoff 4chpro to command 4 independent bulb. Up to today, Each bulb is normally tuned on or off by a relay (so I can use 3 different button to turn on and off the light)

Reading here and there, the most simple solution that is to use the sonoff as a button (itching mode).
In this scenario (please correct me if I’m wrong) HA will never get to know the state of the bulb.

Second option: substitute the existing relay with the sonoff and using the existing button by connecting them to the different GPIOs of the sonoff.
CONS:

  • I canno’t find any instruction/video/pics.
  • Safety…
  • the Sonoff relay will be used a lot, since every time I turn on a light the relay is activated.

Do you have any other idea?

EDIT: I have hass.io running on PI3 and the sonoff is tasmotized.