When multiple characters are banded into battle, the owner gets to choose in which order their abilities activate.
If he chooses to activate a character whose ability causes a SI situation, then all the other character abilities that had not activated yet would be put on hold until the SI is resolved.
So it goes like this:
Player plays banding card (ex. Battle Cry)
Player chooses all Heroes he is banding to with Battle Cry (before doing any abilities)
Player chooses which Hero ability activates first and completes it
Player then chooses next Hero to activate and so on until all abilities are completed.
