The essential nutrients in milk is in its fat. Cream from grass-fed cows is rich in vitamins A, D3, and K2 (industrial pasteurized milk is "fortified" with synthetic vitamin D2, known to be toxic to the liver). Real milk's vitamins (A, D, E, K) and its CLA (conjugated linoleic acid) are fat-soluble, and are transmitted via the cream (they exist in the fat of the milk)...and they cannot be absorbed, nor utilized, without the fat. Low-fat (commercial) milk is always supplemented with vitamins, because they are naturally missing after the milk's processing.
Saturated fat is an essential human nutrient. It builds and strengthens multiple bodily systems, hormones and organs, including the brain and the heart. Inefficient saturated fat intake is a major factor in the modern epidemic scourge of chronic disease and endocrine disruption in our culture.
I've had people tell me that they can't (won't) drink whole milk...they don't like "creamy" milk. This is the ubiquitous adverse palette programming of two generations being raised on skim or reduced fat milk, the unfortunate result of the food industry's "fat is bad" mantra. If you will not retrain your palette to consume whole milk, at least do not relegate your children to the same nutrient-deficient fate.
[In fact, one of the reasons I prefer goat's milk is its natural homogenization. Not well suited for butter making, but excellent for drinking, goat milk is smooth, creamy, satisfying and sweet. Yes, sweet...we've had people say our goat milk doesn't taste at all like "goat" milk. I'm sure this factor varies depending on breed and feed, but we have found that keeping bucks away from the property helps immensely. I've also heard you should not let your goat milk sit for more than 4 days in the fridge without consumption, as the fats will develop that "goaty" aroma. We have not experienced that, though...we consume our milk rather quickly and make yogurt.]
So, if you want your kids to benefit from healthy brain development, strong bones, vital cardio systems, fully functioning hormones, thriving guts, well-developed collagen and cushioned joints, feed them good fats...lots of them! Certainly, you want them to receive and absorb body-building essential vitamins and minerals. So, Don't Skim the Milk! (Unless you're making butter, in which case, you could pour the skim milk onto the earth in your garden for microbial benefit of the soil.)
Why Skim Milk Isn't as Healthy as You May Think
Rethinking Skim Milk
Secrets of Skim Milk