Probably in every culture there are ceremonial and social meals. There are times when eating food with other people creates or strengthens bonds, or when sharing bread or a drink has spiritual significance. One taste of a wedding cake is better than turning down wedding cake altogether, because it's the ceremonial blessing of a marriage. If people are toasting with alcohol and you don't or can't drink alcohol (ever, or at that time), at least join the toast with water. To refrain from joining a toast is worse than an insult; it's like a public curse. One who pointedly fails to toast is standing up against the crowd and saying "I hope your project fails horribly" (or whatever it might be). So let your children know those things.
In the absence of a social obligation to eat at least a token amount, let your children choose not to eat if they don't want to. If the purpose of food is the sustenance of the body and the mind, then let that principle override schedules and expectations and traditions, most of the time. Your children will be more willing to eat to be polite if you only press it on rare occasions.
From "Social Obligations and Oddities," page 168 (or 190)
of The Big Book of Unschooling
which recommends SandraDodd.com/eating/humor
photo by Cátia Maciel