My 3-year-old son has been allergic to milk, eggs, wheat, peanuts, barley and tree nuts. We found out about his allergies after he was tested when he was just about one year since he was having many reactions to foods I tried to introduce. He will drink rice milk and that has worked very well. I buy Rice Dream. I have even found it at Wal-Mart where it isn't as expensive as Jewel or Dominick's. I'm not sure where you are located, but Whole Foods carries MANY foods that we can buy for him. They sell many brands of yogurt that are dairy free.One brand is Stonybrook Farm. I've tasted it and it is pretty good. You can also get ice cream made from soy milk from Rice Dream and, honestly, it tastes very good. Whole Foods is a little expensive, but they have a huge variety and are very helpful. Plus if you get something and your child doesn't like it, they will take it back, no questions.
If he does have a milk allergy, kids often will outgrow them. So far we have had annual blood tests, and no luck yet, but my son is so used to his diet that we function just fine.
The Food Allergy Network site also has good resources including recipes and other good info. http://www.foodallergy.org/
Whole Foods will also have food fairs from time to time targeting specific food allergies.
Good luck with everything. I felt pretty hopeless when we first found out about his allergies, but we have found many foods he can have and once you deal with it, it just becomes a way of life.