"He came home after the class and he ate his dinner."
Translation:Tháinig sé abhaile tar éis an ranga agus d'ith sé a dhinnéar.
...d'ith sé a chuid dinnéir - or dinnéar - I'm not sure which - would that also be correct?
"cuid" is usually used with collective nouns, and plural nouns. It wouldn't usually be used with a singular noun like "dinnéar", but because many basic foodstuffs like arán and bainne are collective nouns (and therefore used with "cuid"), you might make the argument that "dinnéar" could be used that way, but it might be a bit of a stretch.