You're not trying to raise a child who's frightened of food. You're trying
to raise one who can say a single clear sentence to an adult and be
understood. Practice that sentence out loud at home, long before they
need it.
Ages 4 to 7
Make it a rule about bodies, not a punishment
At this age, keep it simple and physical: some foods have something in
them that hurts my tummy, so I eat different ones. Try not to say
"bad food" or "not allowed". Both of those invite guilt, and guilt
makes kids sneak.
Practice this: "I can't eat that, it makes me sick. Can I have
mine instead?"
Send a safe treat in to school and leave it in the cupboard. Then there's
something ready when cupcakes turn up unannounced. At this age, being
left out hurts more than missing the cake does.
Ages 8 to 11
Give them the why, and the word
Now they can handle how it actually works: gluten is in wheat, barley and
rye, my immune system attacks my own gut when I eat it, and the damage
happens whether or not I feel it that day. They'll need that last part
when a friend says "just a little bit won't hurt".
This is also the age to teach that crumbs count. The two that come up
most are the shared toaster and the same knife going back into the
butter.
Practice this: "I have celiac disease. Even a crumb makes me
ill. Was that cut with a clean knife?"
Ages 12 and up
Hand over the questions
Let them do the asking while you're still standing there. Let them order
at the restaurant, ask at a friend's house, and check with a coach
about team snacks. They'll be doing all of it alone soon, and it's
much easier to learn with you a step behind.
Expect them to push back, especially around friends. That's normal, and
it isn't a discipline problem. What helps is giving them some control:
let them pick the restaurant, keep food they actually like in the
house, and treat a slip as something to learn from instead of a
failure.
Practice this: "I have celiac disease, it's a medical thing, not
a preference. Does the kitchen have a way to keep it off the grill?"
The situations that actually come up
Birthday parties
Message the parent a day ahead and send along a portion of something similar. You want your kid holding a plate at the same moment everyone else is.
School
Ask for it in writing. You want a dedicated toaster or toaster bags, a cleaned surface, and one named adult who knows. Keep a safe snack in the classroom cupboard for surprise treats.
Sleepovers
Send breakfast with them. Mornings are usually where it goes wrong. Cereal and toast are what everyone else is having, and both are out.
Friends offering food
Give them a line they can use without explaining the whole disease: "Thanks, I can't have that one, I brought mine." When everyone's watching, short works better than accurate.
Feeling left out
Say it out loud instead of trying to fix it. "It's rubbish that you couldn't have the cake" lands better than a substitute snack and a change of subject.
Eating out
Let them hear you ask about the fryer and the grill every single time. Ask it often enough and it stops feeling embarrassing and starts feeling normal.
This is general guidance from other families, not medical advice. For
diagnosis, testing, and anything specific to your child, talk to their
doctor or a pediatric dietitian.