I think you'll find that 100 Ohm is far too high in value (particularly for a motor). Generally speaking, current detection only requires a very low value resistor so a relatively small voltage drop will occur. A relatively large value resistor will cause a large voltage drop (depending on the current drawn by the load) and this will potentially cause performance issues with the load (the potential across the load might be too low, eg: your motor will run slower). More torque on the motor will also cause more current to be drawn which in turn will cause a larger voltage drop across your sense resistor.
With the load being a motor, as premelec suggested, other forms of spike suppression might be a good idea. In addition to the capacitor/s (and I would suggest several values to efficiently cover a wide band of suppression), zener diodes or 5V transorbs (or other forms of 5V clamps) might be a good idea. You might even need to clamp any negative going spikes. Motors are notoriously noisy and can generate all manner of unwanted signal/noise.