Arduino current

Docedison:
About 10 - 20 mA each for the processors (328 and 16U)

Datasheet says otherwise. 16MHz, 5V gives just under 10mA. (this ignores any load on the I/O pins...)

But as I said before, the only way to be 100% sure of the consumption is to measure it.

If power is a problem then use a board which dumps the second AVR chip and voltage regulator.