Good points guys, the thing that I still don't know is the winding resistance of the coil which will determine the maximum amount of current to be drawn from the capacitors( is there anything else?).
And also I don't know the time exactly that i need the current to be pumped in the coil. After I determine these important factors, I will use Kai's equations to calculate C.
I don't think that the capacitors will be fully discharged, as Kai puts it the voltage drop is just 10% of the maximum value.
I think I have solid grounds now to tacle this design problem, thank you very much for your help.
P.S when I dominate the world I will put Kai as my deputy, and the rest of you will be ministers. :)
Mahmood