Family Tattoo Placement?

Im getting a circular family tattoo tomorrow and I dont know where i should get it. Either lower back or upper left shoulder. I kind of want it shown but I dont know. I also was wondering if there were some symbolic meaning behind the back or shoulder. If I were to get skinnier, would they stretch or is it just if i get fatter. It will be a little smaller than the size of my palm, so 3 inches in diameter. Thank you so much.