Oomis-i have a close relative that has a child with celiac. In answer to quest. 1-no. A person with celiac cannot have any amount of gluten. Even if they won’t necessarily feel the effects,as in this person being asymptomatic,the gluten still damages the lining of the intestine.
And for your second question,gluten won’t cause the same type of airborne reaction,however,you do need to be careful of cross contamination,I.e. The serving spoons,and the stuff on the plates,use separate serving pieces for anything with gluten. It goes without saying that the celiac sufferer cannot have just the soup from the matzah ball soup,as this is cross contaminated.
Hope that helped.