can make a hotkey on every character that occupies the same hotkey slot with their respective epic commands.
/useitem "Name of epic"
then on the driver toon make a social to /bcga //keypress HotKeyNumber
Like, /bcga //keypress 9
Then you hit the key on the driving toon and the others will follow, so long as they're not currently casting/moving (assuming cast time requires you stationary)