As someone with a little photography experience from years of working at a community newspaper, I have some idea of what I like to see in my pictures. When it comes to family portraiture, I like to keep it casual, relaxed poses with plenty of shiny, happy faces in interesting groupings. As I'm looking for images that will display my beautiful children and their family on the wall of our living room, spending too much time on moody little shots of hands, etc. really doesn't suit.
I was surprised then, a few years ago when we last had pictures taken, to see how much effort our photographer was putting in to these types of photos. While I appreciate creativity, it was just not the style I wanted. For example, my son and his wife looked wonderful in one of them; it would have been my choice for framing. The problem however, was that it was only the legs of their three children that were included. An original idea, for sure, and charming, but almost useless when one is looking for a family portrait.
Obviously, different people like different things. It's important, therefore, to know what you're looking for when having a sitting done. Discuss what you want, and what you don't. Be firm. Look at examples of their work and of other people. Don't be afraid to make a suggestion or too if you see something you like. The following links offer some ideas for family portrait poses that might give you some ideas:
50 Outstanding Family Poses
DPS Unposed Posing for Photographing Families Naturally and Fun
Stress-Free Posing, the Family Edition