to my observation, i2c did not work very well with AVR Arduinos to Raspi - perhaps it was a clock stretching issue (using WiringPi and Jessie releases from 2016); OTOH, the Due always worked very well, up to 1.5m cable lenght, including the Due, a RTC, and an IMU. But perhaps this AVR issue is meanwhile resolved with the new Linux kernel used by Stretch.
Nonetheless for your task I would work with UART instead, and for long distances I would choose 2x HC-05 interfaces in between. The HC-05 on the Pi also works at the USB ports, and having e.g. 3 HC-05 pairs at 3 different USB ports plus another one at the serial0 UART will provide you all over 4 serial connections to 4 different Arduinos.
And when you'll plug an USB hub to your Pi, then even some more... what would you think about that?
ps,
in case you had many many more than just 4 clients to host, then perhaps consider using a web interface. The ESP8266 nodeMCU works very well like stand-alone Arduinos (it can be programmed directly by the Arduino IDE just like Nanos) and can communicate to web servers via different WiFi or ESP8266web client/server libs to the Pi.
The Pi may work as the webserver then, but tbh, that's not always trivial to program.
So you might like to connect an additional nodeMCU to the Pi via USB/serial or i2c and use this extra one working as a ESP8266 web server to all those ESP8266 web clients, either one using the handsome Arduino libs. And not to forget, 1 ESP8266 costs just less than 5 EUR each.