Best communication option for multiple arduinos?
According to me using moteino with accelerometer module like MPU6050 would do the trick. One use was able to get a range of 1.5Km using moteinos(https://lowpowerlab.com/forum/moteino/rfm69hw-driverange-test/). You will have to decide the frequency of data that you get, so accordingly the system can go in low power mode and give a longer battery life.