Thanksgiving dinner is unusually hostile to a picky eater: everything is unfamiliar, served once, and eaten in front of an audience.
A bread roll, plain rice, or something you know they eat every week, sitting on the table alongside everything else, is not giving in. It is the difference between a child who eats something and a child who eats nothing, in front of everyone.
"Just try one bite", said by three different relatives, turns a plate of food into a performance. Serve the plate, say nothing else about it, and let the meal be about the table, not about what is or is not being eaten.
A small plate they assembled themselves — even if it is two rolls and a piece of turkey — gets eaten far more reliably than a large plate an adult served for them.
Thanksgiving, with extended family watching, is about the worst day to introduce a new food. Save that for an ordinary Tuesday when nobody is keeping score.
A short, flat "they are fine, thanks" and a change of subject works better than an explanation. An explanation invites a follow-up question.
Part of our guide to Holiday hosting with kids.