If a Dark Elf has two Slave Pens in play , Kingdom and Quest , a Shades unit in play and decides to use the 0 cost tactic Whip the Slaves . Sacrificing the Shades , does the DE player get power on both Slave Pens AND draw cards from the tactic played ? I guess I'm asking if one sacrifice play benefits all sacrifice rewards on the table ?

You can only sacrifice a unit for one of the effects, so if you sacrifice Shades for Whip the Slaves, you cannot sacrifice it for Slave Pens.