I am trying to think of good techniques that can capture the full vibrant scene of outdoor night or poorly-lit events at wide angles.
In my previous experiences, flash fitted with wide-angle plate or diffuser is usually still not enough to illuminate an entire ballroom nicely, and certainly cannot brighten the outdoor environment. Depending on the size and configuration of a ballroom, i may still be able to get away with bouncing flash around walls or ceiling. But usually the far end of the background remains dark and poorly lit.
Alternative attempts is to utilise 2nd/rear curtain sync and allowing the shutter go slower than the set flash sync speeds (typical Aperture mode). This allows the cam to capture dark/night scene as seen by human eye while lighting up the foreground subjects at the last moment to freeze their "final state". Of course this is subject to plenty of handshake and motion blurs, and images won't be as sharp as with fast shutter speeds.
What are some other ways to capture decently stop-motion pictures in dark open spaces?
UPDATE - my operating style
To better understand my situation I should explain my setup. To cover events with high mobility, I sling the BlackRapid DR-1 strap to wield two EOS 7Ds, one wide-angle with a 10-22mm f/3.5-4.5 and the other telephoto 24-70mm f/2.8 or 70-200mm f/2.8 depending on environment size. I have 580EX II and 430EX II. I am not working as a professional. I also do not make use of any full-frame as I do not recognise any artistic progression I can get from that after putting in extra money.