Hi,
To enable/disable a script you can find an action on the
Ecosystem called "Enable script"
If the enemies need to idle and only react within a certain range i would do something like this :
Have child object with a trigger on the player and set the size that the enemies should react.
On the enemies have a fsm that gets triggered when in range of the player
From the player send an event to the enemy when inside the trigger.
if the player has the powerup send a different event to the enemy.
You can check out
this topic this does something similar to understand the basic.
I am traveling atm, if you want i can make a sample in a few days.