One important consideration if using high voltage capacitors is to step the voltage down before powering the motor.
The most efficient way is to use a DC-DC converter. However, finding one with an output voltage as low as 2.4V and which also allows an input voltage of 250V will be an interesting challenge. You might be able to modify a small mains powered power supply, but note that they already probably have more than 47uF of storage on the high voltage DC side and they don't last long once you remove the power.
For very low power situations you have the problem that the current required to power the electronics (from the high voltage side) may be higher than is required (again, from the high voltage side) to provide the amount of power to your load.
Using a high voltage is not such a bad idea, since the power stored in a capacitor is proportional to the square of the voltage. Because the thickness of the dielectric is proportional to the voltage, and the capacitance is inversely proportional to distance, things balance out such that the total energy storage is pretty much linearly related to volume for capacitors using a given dielectric. There are other factors which vary, but this is a disappointing rule of thumb.
Super capacitors have a dielectric which is far more "efficient" in terms of space. However these are only available in very low voltages necessitating multiple capacitors in series to withstand a larger voltage.
Before you think that 2 of these in series can withstand twice the voltage (true) and thus store 4 times the energy (false), remember that placing n equal capacitance capacitors in series reduces the total capacitance to 1/n. Once you combine the fact that with n capacitors in series you can withstand nv volts with a combined total capacitance of c/n you'll discover that the total stored energy is proportional to the number of capacitors.
Having a single high voltage capacitor has one significant advantage, you do not need to worry about balancing the voltage across multiple capacitors. As the capacitance of the parts of a series string of capacitors rises, the amount of energy which must be transferred to maintain the balance also increases. If one does not wish to simply dissipate this energy, an active solution is required which can be quite complex. (zener diodes are a simple, cheap, and relatively efficient method for moderate power levels).