That was my first thought too. Justin had a very limited diet- by his choosing- consisting mostly of mac-n-cheese, cheese sandwiches- the exact things that I needed to cut out. What would he eat?
He has more than just the gluten and casein going on, though, we found out. Quite a few IgG allergies.
Well, wheat & gluten are out. But he is okay with rice, potato, corn, and soy. (corn is iffy for some kids, though, and soy still isn't a good idea, so both of those are very limited at our house) The good thing is, that there are plenty of gf products on the market now. I can find rice pasta at Wal-Mart, even. And things you think should be gf sometimes aren't, you have to be very careful, like regular Rice Krispies. You'd think they'd be okay but they have malt flavoring. But there are plenty of things available once you start looking. I buy gf bread mix and use the bread machine, the health food store carries pre-made stuff but I prefer the bread machine bread. I buy some of the food from
amazon 'cause it's cheaper, but you do have to order it in bulk, so best for cereal, bread mix, stuff you know you'll need.
Dairy is the same deal. Many stores carry soy milk now, but we don't do soy. We do rice milk. There is also a potato-based milk. The health food store carries rice "cheese", rice "ice cream".
There are some things you can't find a work-around, and you end up cooking from scratch much more. There's a learning curve involved, but once you jump in, you get the hang of it. I'm no Betty Crocker and we managed.
We do a calcium supplement. I get his from Kirkman, it is a powder so I can dump it in a drink. We also use Kirkman vitamins, and a ton

of other things.
http://www.gfcfdiet.com/ go to the bottom of the page, where it says Directory, click there, there is a huge huge list of gfcf food. Like a whole notebook's worth. I printed it all out, all of it, and went thru it with a highlighter for the things I could buy at a "normal" grocery store. There is also a gfcfkids Yahoo group that is very active, typically 4 or 5 daily digests a day, lots of good info.