Ideally, raw whole milk would be best. Failing that, then alternate between organic whole milk and some kind of organic, unsweetened fermented milk such as kefir or yogurt. There are many ways to prepare it to make these more digestible and less mucous forming, such as simmering the whole milk for 10 minutes, but this is not always required. It really depends on the child, how they take to it. It's tough to only drink fermented milk, it can cause cramping, and it's tough to only drink whole milk because of all the milk sugars.
you can also take cottage cheese and blend it up with rice or almond milk. Check the Nourishing Traditions cookbook out for lots of homemade recipes for children. :)