Hi! I am shooting an outdoor Vacation Bible Camp next week and they want me to take group photos. I'm assuming that these "groups" are going to be fairly large since they have about 600 kids attending. I have a Canon 30D (so we're talking a crop body) and will have a 10-22, 24-70, and a 70-200 (and a nifty fifty). Could you please advise me on which lens and focal length is best for this situation? Thanks so much!