Next week I am experimenting with a few families shooting on what may be midday on a sunndy day. If the sun is in full force, I plan to put the sun behind them as best I can and use a reflector. I am going to be in an open field so artificial lighting may be a challenge due to lack of electricity and I don't have a battery powered speedlight. Anyway, I have 50" sliver/white reflector. How big of a reflector do you think I need for a family of 4 sitting on the ground or standing close together?