Gluten Free Cookbook

fruit, some brands of corn flakes, most vegetables, meats. Avoid anything made with wheat or wheat by-products. Read labels.
References :

Unprocessed meat, fish, eggs, nuts, fruit and vegetables, plus rice and corn, are all naturally gluten free. Most processed foods, unfortunately, have gluten added to thicken/coat or flavor the food (eg. as malt).

Your son may like fruit, dried fruit and things like trail mix. Fruit leather is usually made with just fruit, and most kids love it. You can also make up a fruit jelly/jello mix and maybe put some canned fruit in it. Most people I know love this, whatever their age.

For main meals, go back to traditional meat and 2 veg, make gravy yourself thickened with rice flour or cornstarch, and you will be fine. You can also make an omelette, ordinary pasta meals (substituting the pasta for gluten free pasta – Orgran is a good brand, and using gluten free flour for thickening of any sauces, if you need to), and one-pot rice meals like risotto or jambalaya (make sure the sausage and all the other ingredients are gluten free).

If he has a liking for cheese and dairy products, it’s best to try and wean him off this, as casein (a milk protein) is also damaging to autistic children. Rice milk, almond milk and other nut milks are good substitutes for dairy milk (soy milk also, but this is another problem food, best avoided as much as possible, if only because of its hormonal effects in large quantities).

The gluten free, and the gluten free/casein free diets are not too difficult if you first clean out your kitchen cupboards and then start slowly with basic stuff, adding different things as you find stuff that works for you.

The most important mantra you need to follow is: Check the Label of Every Pack Every Time You Buy. You need to check every pack, every time, because manufacturers often change ingredients without any warning or mention on the front of the pack (if price or availability of some ingredient changes), but the ingredients label will tell you.

If you have difficulty recognizing gluten in lists of ingredients, this article should help: Master of Disguise: How Gluten Hides Where You Least Expect It: http://okget.info/about/GlutenHides
References :
http://okget.info/about/glutenFAQs
http://www.GlutenDairyFree-Easy.com recipes