The milk with the fewest calories and the least fat is the skim milk. But is that then the best milk? For children under two it is absolutely not the right choice. Children under two still need all the fat and calories that come from whole milk, and this is what they should drink (the developing brain in young children needs the fat and cholesterol that is in whole milk).
For older children and adults however, whole milk can be a source of unwanted calories and fat, particularly in this era when so many of us are overweight. High cholesterol is also an issue for many of us, increasing the risk for heart disease. To make matters more complicated though, there is certainly recent evidence to suggest that a diet with absolutely no fat or cholesterol is also not the best!
So what is the right answer? Probably for most of us, one percent milk makes sense if we are drinking a glass of milk or pouring it onto our cereal. Some people find it too watery to use in their coffee or tea, and then 2% milk is fine to use. I can't think of any good reason for adults to drink whole milk (except that it's what many of us are used to and its hard to change!). Thus for your family with older girls, one percent milk should be fine for everyone.
It is important to note that all these different types of milk have pretty much the same amount of vitamins A and D, as well as calcium. All of them will provide what older children need for continued growth and strengthening of their bones.