I think oftentimes when scheduling a photo shoot for ones family the ultimate goal is to just have everyone looking polished, clean and present. Themes? Too much work. Unique looks? Oh the anxiety! It is in these situations that a simple classic wardrobe works best. I am partial to getting a little dressed up.
So start with a base color scheme. I personally like dark colors for a more dressy look. Then throw in a couple pops of color. Shoes, hair accessories, ties, and hats are all perfect areas to insert a color. In the collections i put together I have the men in jeans. But if you really want to go full on semi formal for this, then put the men in a pair of slacks and it will still look wonderful. Oila! All of a sudden your family will look worthy of any picture above a mantle!