I think of this expression as meaning something like 'have gladly', except that, unlike the adverb 'gladly', 'rád' must be inflected.
Kids are tricky (if you have one you know it is true). Dítě is neutral in singular and female in plural... kid you not. But then, look at English - Child vs. Children. Irregular. All over the place
I guess from this sentence that Czech uses verb "to have" for affirmation. English uses verb "to do": Children do like sugar
No, "mít rád" means simply "to like".
For affirmation you can use "opravdu" or "skutečně" (both translated as "really"), for instance "Děti opravdu mají rády cukr."
I translated this as 'Children like to have sugar', but shown as wrong, 'Children like sugar' - is Deti rady cukr' not enough?
No. Rád is in reality an adverb. Not a verb. MÍT RÁD together means to like.
If it were an adverb it would not change with gender. It is an adjective, although in an old form.
What are all of the forms of rád-? Like what are all the potential endings that I have to tack on and when do I do so?