This article might be helpful. It breaks down each type of test, and what a positive results means in terms of the probability that you might have celiac disease. Re: tTG-IgA:    

Most antibody tests for celiac don’t report a zero because of the way the tests work.  The lowest reportable value is usually <# (# being the lowest quantifiable value for that particular lab’s test).  Values can and should eventually decrease into the normal range.  So for the lab used for your son, a 9 would be considered normal. A grain of wheat will not trigger the same response as a full bowl of spaghetti. Most biological reactions follow a dose response curve - the larger the dose, the larger the response - in that particular person. The intestines can be attacked and antibody levels can increase without symptoms.  Also, acute symptoms from a one time “glutening” can happen without antibody levels increasing. The severe acute reactions that some people have within minutes to hours after ingesting gluten appear to be due to cytokines. I call myself a supersensitive but silent celiac.  I never had obvious symptoms but was tested because I get migraines and my doctor thought there might be a connection.  I do have less fatigue now that I am gluten free.  Still get the occasional migraine unfortunately. I started my gluten free diet by avoiding things with obvious gluten ingredients,  Antibody levels went down but one was still above normal.  Then I only ate processed foods labeled gluten free. That antibody level decreased more but was still above normal.  Now I eat processed foods that are certified gluten free or small amounts of a few items labeled gluten free from very reputable companies and all my antibody levels are in the normal ranges. The stubborn antibody level rose above normal once, I stopped using gluten free flour from a reputable company and it went back down to normal. It would almost be easier if I DID react obviously to gluten.  Then I’d know what foods to avoid, instead of relying on once a year blood tests.      

As a parent myself, I find we feel these things very keenly, it is completely understandable that you feel the way you do. It won't always be easy for your son, of course, but honestly most of the coeliacs I know are very healthy individuals who enjoy life to the full and have adapted very well.  Family support is a massive factor in this, and your son has a wonderfully supportive family which will give him the best start possible.  He is very fortunate to have such an understanding mum.   On the response to gluten question you posed earlier - yes, many people when they come off gluten completely, after a while when they are exposed to gluten by accident or intentionally they react much more strongly than before, compared to when gluten was regularly being ingested.  I read once that once stop eating gluten completely, it is a bit like your system is fully rested, like a resting army, so when gluten does appear your body it goes all out to deal with the "enemy", throwing everything it can at it.   I am sure someone more scientific can better explain this to you.  But that said, I do have a friend who was diagnosed with coeliac disease just a few weeks before me, is strict with her diet, and she NEVER reacts physically to gluten, bizarrely.  It does happen! As regards blood tests which your son will no doubt be offered, these are to check for compliance to the gluten free diet as well as to check no other health issues are arising.  But on that first point, the blood test is unlikely to pick up one or two glutening experiences that happen in a year,  it tends to be more helpful to show if there is regular cross-contamination or ingestion of gluten.   When I was unintentionally taking an iron supplement that had gluten in it, it was a blood test that drew my attention to the fact that something was going wrong with my diet.

Well, we have an appointment with a pediatrician who specializes in gastrointestinal issues, and subsequently an appointment with a nutritionist on December 6d. So till then it will be google for the win I guess... I have already found a lot of reassuring alternatives for most of his favorite things, which puts my mind at ease. Now we're just having to see how we will navigate the skitrip in march in an all-in hotel and food on the slopes. And how we will manage offering him warm meals daily as he used to eat at school as we can't manage to cook in time before his soccer practice starts as our commute doesn't allow for it... That kind of thing. But we will manage in the end.   I do feel a lot of sadness for him though. He's so small, will never remember the time before the diagnosis when he didn't have to see (some) food(s) as the enemy and even thought that is comforting in a way, it also is quite sad as a notion... I know we now have the opportunity to help him in the best way and help his health, I do. But I also grieve. I can't help it.

I’m having a terrible time with my employer on this, they put me in an office next to where everyone places food for the department and have reactions when foods containing gluten are present. I’m extreme celiac and have a reaction in some bakery isles at the grocery store. Airborne gluten reactions are real in my world.