I see you have had many, many responses about waiting till your son is at least 1 year old or more to introduce cow's milk - yep, exactly. However, I didn't see that anyone had mentioned raw milk - it's second only to human milk as a great choice to feed our babies (and it's great for all ages). Raw milk is without a doubt the most nutritionally-viable form of cow's milk to offer (especially for a baby's immature system) - our whole family drinks only raw milk and loves it. It's available at Whole Foods and possibly other health food outlets, and can be ordered directly from Organic Pastures (near Fresno) if needed (www.organicpastures.com). On their website you can also read about the nutrition facts etc. Also check out http://www.realmilk.com/where1.html to find out more about where to get it (and there are other links where you can read more about why to use it, etc.).
When you introduce cheese, raw milk cheese is also the best way to go - again, it's available at Whole Foods for sure; we have used both raw cheddar and raw Monterey Jack and they're both delicious!
You can make the most fabulous homemade ice cream using raw milk and raw cream (yep, also from Organic Pastures) - it's way better than ANY storebought kind (I can post a recipe or email it if you're interested in trying it). We've made it for summer cookouts and parties, and everyone always raves about how good it is.
Anyway, hope this helps in some way. I was sooo thankful to find out about the benefits of raw milk and I only wish I'd known sooner - that's why I wanted to post this info here for you. :)
Blessings,
S.