I do plenty of group shots and I don't really see you asking the two most important questions:
1. Lighting-- what time of day will you shoot and how will you light them?
2. Posing-- will there be someone-perhaps you-to keep everyone in place and make sure everyone's face is visible?
I say you'll need at least 5 helpers not posing in the image to help keep order. You're dealing with many people and animals.
Where will you be taking the image? Is there somewhere you can high and shoot downward so as to get the back row's faces in the frame or will it be a group shot one deep and just a long line as shown above?
Nikon D700/D300|17-35 f/2.8, 24-70 f/2.8, Sigmalux, 80-200 f/2.8, 16 f/2.8 fisheye,
Lots of flashes and Honl gear.