Oh, the design question :)

"Small enough to get it charged"

"Bit enough to get the output power required"

There is some tradeoff: higher frequencies allow for smaller capacitances, lower source impedance allows for higher capacitances (resulting in higher output power available).

If anything else is well-defined, you can "play" with the values. Typically, all capacitances are the same value. Then look at the charging curve (voltage "over" the cap) and at the output voltage (effects from the load).

Wish you success