IMO, in oder to take advantage from positive properties of gyroscope and accelerometer, you need to use a sensor fusion. These can be done by using the KF. In these case, a gyroscope and accelerometer are used together to create a more accurate measurement of overall movement and location through space.
Here you need to use the state vector with 6DOF:
X=[x, y, z, x", y", z"]
So your system matrix A is a 6x6.