Group Young Child Party Photographing

I've been roped into doing a childs party group photo in what will be a fairly poorlylit clubhouse, I have not done this type of photography before and am looking for advice. A round about 35 4-6year olds, I have a canon 5d3 with 24-105l lens and a Metz 44 AF-1 flash. worriedly needing advice.

I'm afraid I won't be much help, but you need more than advice my friend. Get lots of adult help. Trying to get that many kids that age together for a photo will be like herding cats. I've done it a couple of times and it's a crapshoot. Good luck.

Rules I usually follow for kids B'day shoots.....

Rule #1 - Get to their height. (Sit / Kneel / bend / Do what ever it takes to get to 3ft )
Rule#2 - Carry Zoom - 24-105 will do good. I would keep 70-200 handy as well
Rule #3 - Always keep looking through the view finder, kids will be better with natural poses. You never know when is the right moment...so keep looking through your camera continuously

Good Luck with the kids!