A multivitamin is great.  Multivitamins contain lots of trace minerals we need.  My only hesitation is that many use thiamine mononitrate which is not easily absorbed nor utilized by the human body.  Thiamine mononitrate is used because it's cheap and shelf stable.  You can add in a thiamine hydrochloride or a Benfotiamine supplement in addition to the multivitamin.   I would give a multivitamin to all the kids.  Even the ones without triggered celiac disease.  Kids do a lot of growing, even into their early twenties, and need plentiful B vitamins.  The gluten free diet can be low in the B vitamins.  The B vitamins are water soluble and easily excreted in urine if not needed.  The...