Both my kids are allergic to milk. So they didn't get calcium or fat or ptotein from milk, cheese, yogurt, butter, etc. And they are fine. I use soy milk in recipes. Low in fat (great for me!), but high in protein. For fat, I used other sources. Meat, oils, nuts.
I read from someone on here to watch out with rice milk with boys because of high estrogen levels. Also, rice milk offers very little nutritional value. Soy milk has more vitamins, minerals, protein, a bit more fat and calories.
The idea that humans NEED cow's milk just isn't true. There are so many other sources out there for your son to get what he needs.
And if it is just the milk he doesn't like, just up his amount of cheese/butter/yogurt. Just make sure it's the good fat and not the ice cream sort of fat.
As for calcium, you can buy soy milk with added calcium and vitamin A and D. Because the kids are allergic, it is WAY cheaper to make our own soy/oat/nut milk. Oh! Almond milk is also very good. Anyway, we make our own, so vitamins aren't in there. But if he is eating fruits and veggies, he's going to be getting what he needs to survive. Just go on a website that shows what vitamins and minerals are in fruits and veggies and make sure he gets a wide variety.