Candids have been my mainstay. For myself, I find it hard to both take pictures and take part in the activities becuse of the way I approach them. One of the trickiest things is trying to have people not notice you. I try to blend in with the background and keep my eye open for opportunities. You are going to have an advantage because this is going to be an event. It won't seem weird to have a photographer there.
One of the tricks I've learned is to stand in a very relaxed way. If you are looking around for a shot in an obvious way, you are going to come across like a hunter and people will notice. They are more likely to either avoid you or ham it up, neither of which is very natural.
I tend to keep both hands on my camera with them in the shooting position, so I'm ready to pop it up to my face at a moment's notice. I also keep the camera at my chest, rather than down on it's strap. This could easily catch people's attention, but I tend to cradle it there with the lens pointed downward in a very relaxed manner. I avoid looking people in the eye or directly at them. This combined seems to give the indication that while I might be looking for a shot, it's not them (even if it is). Having the camera up high all the time will also attune people to seeing it up there. When I put it up to my face, it doesn't grab attention like it would if I kept my hands by my sides and the camera hanging from the straps. So I just wander around, lost in my own little world, ignoring people, but still watching everything. It's worked really well for me.
