Thank you mfalkvidd, I did it and it is working well now!.

For those who want a simple solution and as future reference, here is my simple code:

#define MY_DEBUG
#define MY_BAUD_RATE 38400
#define MY_RADIO_NRF24

#define MY_RF24_PA_LEVEL RF24_PA_HIGH
#define MY_RF24_CHANNEL 115
#define MY_RF24_DATARATE RF24_250KBPS
#define MY_RF24_BASE_RADIO_ID 0x00,0xFC,0xE1,0xA8,0xA8

#define MY_NODE_ID 164
#include <SPI.h>
#include <MySensors.h>

#define RELAY_PIN 2  // Arduino Digital I/O pin number for first relay (second on pin+1 etc)
#define NUMBER_OF_RELAYS 1 // Total number of attached relays
#define RELAY_ON  1 // GPIO value to write to turn on attached relay
#define RELAY_OFF 0 // GPIO value to write to turn off attached relay


#define RELAY_CHILD_ID 1   // Id of the sensor child RELAY
#define MOTION_CHILD_ID 2   // Id of the sensor child MOTION



#define DIGITAL_INPUT_SENSOR 3   // The digital input you attached your motion sensor.  (Only 2 and 3 generates interrupt!)
uint32_t SLEEP_TIME = 10000; // Sleep time between reports (in milliseconds)..NOT USED ANYMORE BECAUSE IT TURNS OFF THE NODE AND IT CAN'T RECEIVE RELAY REMOTE TRIGGERING ORDER

boolean lastMotion = false;

// Initialize motion message
MyMessage msg(MOTION_CHILD_ID, V_TRIPPED);

void before()
{
    for (int sensor=1, pin=RELAY_PIN; sensor<=NUMBER_OF_RELAYS; sensor++, pin++) {
        // Then set relay pins in output mode
        pinMode(pin, OUTPUT);
        //Always starts OFF
        digitalWrite(pin, RELAY_OFF);
    }
    pinMode(DIGITAL_INPUT_SENSOR, INPUT);      // sets the motion sensor digital pin as input
}

void setup()
{

}

void presentation()
{
    // Send the sketch version information to the gateway and Controller
    sendSketchInfo("Relay_PLUS_PIR", "1.0");

    for (int sensor=1, pin=RELAY_PIN; sensor<=NUMBER_OF_RELAYS; sensor++, pin++) {
        // Register all sensors to gw (they will be created as child devices)
        present(sensor, S_LIGHT);
    }
        // Register all sensors to gw (they will be created as child devices)
    present(MOTION_CHILD_ID, S_MOTION);
}


void loop()
{
    // Read digital motion value
    bool motion = digitalRead(DIGITAL_INPUT_SENSOR) == HIGH;
    if (lastMotion != motion) {
      lastMotion = motion;
      Serial.println(motion);
      send(msg.set(motion?"1":"0"));  // Send tripped value to gw
    }
    // Sleep until interrupt comes in on motion sensor. Send update every two minute.
   //  NOT USED
    // sleep(digitalPinToInterrupt(DIGITAL_INPUT_SENSOR), CHANGE, SLEEP_TIME);
  //  NOT USED
}

void receive(const MyMessage &message)
{
    // We only expect one type of message from controller. But we better check anyway.
    if (message.type==V_LIGHT) {
        // Change relay state
        digitalWrite( RELAY_PIN, message.getBool()?RELAY_ON:RELAY_OFF);
        //digitalWrite(message.sensor-1+RELAY_PIN, message.getBool()?RELAY_ON:RELAY_OFF);
        // Store state in eeprom
        saveState(message.sensor, message.getBool());
        // Write some debug info
        Serial.print("Incoming change for sensor:");
        Serial.print(message.sensor);
        Serial.print(", New status: ");
        Serial.println(message.getBool());
    }
}

Regards!