Well for this upcoming event I feel pretty comfortable with it for the most part (other than the fact it is so large which is new to me). It is completely indoors with even florescent lighting everywhere (thus I control the lighting as I will be having my own external light with me.... going to bring my flash on a lightstand with a softbox attached and carry it around with me). It is mostly candid shots (which is my strong point) and all posed photos are at the photo booth (where I will have my key light and fill light setup in advance). So this volunteer event is one that I feel pretty good about actually. The last one was outdoors as it was getting dark and the light was different at every angle I turned, so I was constantly adjusting my settings of my flash and my camera. This event will be pretty even throughout lighting wise. I am looking forward to the experience though, as all photography can help me grow and learn more everytime. I do want more in the experience department as I think that will help me not to make those silly mistakes that I still occasionally do. That is a matter of experience and continued practice I think. You are correct though, even for volunteer it does have a cause and it is important to do well. The cause is for a good one and they do have expectations (rightly so) as well.