Translation:A couple of children are playing in the park.
Does it mean a couple like 2, or a couple like in a few? I thought the first and said "A pair of children...", which should then be accepted too.
What you said seems contradictory, but I assume there is no clear translation (that's the same in German, where depending on the writting it's two or a few). But then my answer should still be accepted, or not? How would you say a pair of kids otherwise?
'A pair' is also accepted, but cc08_ is right, in this sentence it means "a few".
My issue is that the word "pair" is a singular noun, therefore needing to have its verb conjugated as such.
"pair" can be either singular or plural in English and usually depends on a larger context. "A pair of jean is" always "A pair of contestants are" or a "A pair of contestants is" actually connote different things. The singular usage implies they are from the same team or are working together the plural implies they are competing against one another. "A pair of children is" or "A pair of children are" are both acceptable and usually the singular would connote familiarity.