My grandfather is celebrating his 90th birthday with a dinner in a restaurant. I'm taking the picture of 10 adults and 8 children (8 years old and less). I am going to use the restaurant's reception area for the picture and the lighting is dim indoors.
I was thinking of having my grandparents and parents sitting on chairs, the 3 couples behind them, and all 8 children sitting on the floor in front.
I plan to use my 1Ds (MkI) on a tripod at a medium ISO 400 setting, 24-105L set probably at f/8, and 580EX flash on E-TTL mode and set as master (aimed at the ceiling). I have two 420EX that I can use as slave.
Q1) Where would be a good position for them? One behind the group for hair highlight and the other from the side? Place them on opposite sides to eliminate all shadows?
If I want to expose the restaurant's background as well, I will need to set a slow shutter (I will probably be using M mode).
Q2) Is there any risk of getting motion blur even though technically everyone will be "frozen" by the flash, prior to the longer exposure of the background?
Q3) Is ISO 400 and f/8 adequate for three rows?
Any other suggestions or warnings for this very important event?
Thanks a lot for any help.
