Hello,
Deep Kapadia here from Ahmedabad, India. Professionally i'm Embedded System Developer.
I have good experience with ESP8266 based SoC. I have worked with Counters with Internet gateways, ESP8266 based Server.
I can suggest you best ESP8266 variant for this application. Design circuit diagram, Firmware for each nodes and central ESP8266.
Regards,
Deep Kapadia