The timing on this really does suck. I'm sorry.
It can be a tough transition, but it is doable. For awhile, we were dairy/soy/egg/nut free. We really learned to cook all our meals from whole ingredients, and it was a good learning experience for us, and our whole family is better off now. It can be expensive to buy the allergen free processed foods, but if you try to stick to real food naturally soy/dairy free, it is not too bad. Eating out is difficult, though, with the soy aspect. I will say that trying to cut out wheat/gluten and corn is actually much harder, so this allergy combo isn't the worst.
Here is a website that offers meal planning and recipes, which we've found helpful. It can all be modified easily for dairy/soy-free. http://www.tfrecipes.com/forum/index.php
Also, many people have found that dairy-allergic kids can drink raw milk. Or at least raw goat's milk, so that is something to look into, if you live in an area with access (it depends on your location and state laws vary).
Read labels carefully. Many rice milk products still have soy lecitin. I think Rice Dream is usually good. I did find one dark chocolate bar --Lindt-- that doesn't have milk or soy, however it is "manufactured in a plant" so it would depend on your ds's sensitivity level. Enjoy Life chocolate chips are good.