Sending a value from one arduino to another

You could have the LCD Arduino be an I2C master and all the weighing Arduinos be slaves. There's an example of master/slave communication and wiring here: https://www.arduino.cc/en/Tutorial/MasterReader.

I2C supports up to 128 devices and the wiring is very simple.

Yes it is possible,The answer provides one of the basic methods to do so

Connections

   Arduino1          Arduino2
     TX--------------->RX
     RX--------------->TX   

Arduino1 Sketch:

void setup(){
 Serial.begin(9600);
 delay(2000);
}

void loop() {
 ////read sensor data to a variable 
 Serial.println(sensorDataVariable);
 delay(2000); //Not to flood serial port
}

Arduino2 Sketch :

int byteRead;
void setup(){
 Serial.begin(9600);
 delay(2000);
}

void loop() {
  /* check if data has been sent from the computer: */
  while (Serial.available()) {
    /* read the most recent byte */
    byteRead = Serial.read(); //now byteRead will have latest sensor 
                              // data sent from Arduino1
  }
  //Write code to display the values to LCD
}

hope this helps