taking pictures

I don't know why people ask me to take pictures of their family.  I'm not that good.  It makes me nervous. I agreed to take some pictures of a family in our ward today, this will be the first time there is no one under the age of 12 so that will be a little easier.  Wish me luck.  Oh, and they want to pay me.  I never charge anybody, what would you pay someone who is not a professional, but occasionally will get a good shot?