So you take wheat literally? .... did you just look for the word 'wheat' in your bible to support this silly enforcement on communion? Put John 12:24 back in context, my friend, and read it again.
Teff in Ethiopia has been the dominant grain used for making bread and would be understood in Amharic in the way "wheat" is used in English although Teff is not wheat precisely. Those who suffer from celiac sprue disease in many cases do not have any reaction to Teff (or amaranth), and it would be worth exploring with the appropriate dicastery the use of a Teff based Communion host by bringing together secular scientific competence with ecclesiastical liturgical historians as well as others. Such a decision requires more minds, with greater expertise and broader vision. If Teff is not suitable, then there is amaranth, and certainly there are questions about the use of common spelt and the relatively recently discoverd Etruscan spelta for Communion hosts that should be made clear as well.
If an answer cannot be worked out within the Latin rite -- and that would not be surprising to some -- then perhaps the Ethiopian Catholics or one of the other Eastern Catholic Churches might have an answer for a child suffering from this terrible disease.
I would think this is worth exploring bearing in mind the tremendous responsibility to Our Lord and to the souls for whom He died.