Maybe you should consider changing this translation because it's a bit ambiguous. This way, one might think that there are two carrots and some potatoes in the soup. Maybe "There are both carrots and potatoes in the soup"?
So does idir ..agus mean both
Idir X agus Y can mean either “both X and Y” or “partly X, partly Y”.
Or "between X and Y", as most learners expect.
Since cairéid and prátaí are both lenited in this exercise, it would be a mistake to expect idir to mean “between” here.