today i decided to try the shift register approach and see if it was a viable option or i need to turn to charlieplexing.
my 2032 battery was dead, so i used to AA batteries instead, and it work, it has enough juice to power up a standard Arduino, shift registers, and LEDs.
if i power it up from 5V USB each led sink about 50mA, that's a lot of current, but manageable if it flashes fast enough.
but with the AA batteries, it sinks just about 16mA, that's great, so it means, no current limiting resistor.
this is the great think about using AA or 2032 batteries :D