Am planning on taking a sports group formal shoot and was wondering if a flashgun would prove useful? It will be shot in the late afternoon, so there should be ambient. I would like to use flash to catch- their eyes, so would like to use Av mode. The group will be of about 11 people, so I plan to shoot standing back a little way shooting with a 50mm which will give me a 80mm focal length.
Being that I will need to stand someway back to shoot, should I bump the up in order for the flashgun to 'reach' the subjects eyes? Or if for example I was to use 100 or 200ISO will the flashgun compensate and give more power output after assessing the distance of the subject?