Posing Ideas for Group of 10

I have a family shoot coming up on Sunday.  The group consists of 10 individuals. The central person being "Grandma"....Grandma is the main client's grandma but is also Great Grandma/Mom to others.

So, there is Grandma (70+ years), Grandma's daughter and her Husband (50+years), Grandma's 2 Grandsons, 1 Granddaughter, the grandson's wives (20 - 35 age range) and 2 great grandchildren (under 10).

I don't want to do anything really formal, nor do I want to sit everyone on bales of straw with pumpkins and gourds around them....so, any ideas as far as posing...something different with Grandma being highlighted as the Matriarch.  Oh yes, Grandma can walk and stand but for short periods of time only....other than that she is in a wheel chair.  We will be doing this outside at 2:00pm as I cannot accomodate a group this size in my studio...