If you're Airtran Elite, call and they'll make you A-list. With that, you're essentially guaranteed to be an A -- and you don't have to worry about checking in at exactly -24 hours or paying for auto-checkin. I don't think I've been lower than A30.
So as long as you're there when your group boards, you'll for sure have space to put your camera equipment with you.
The other good thing about Southwest: because first bags are free, the masses that travel SW check bags -- so there is usually available overhead space unlike airlines that charge for even the first bag.
Southwest is no where near as good as Airtran, but for what you use it for, it should be fine.