So the singular for boy is Chlapec and why is the plural Chlapci instead of Chlapeci? Dekuji
My answers were "The boys are currently small" and, as a second try, "The boys are still small." I believe both are better than the "correct" answer. "Now" implies that they weren't small before but they recently have become so. It seems unlikely that they are shrinking!
My reading of the current main translation (The boys are little now) is just the opposite of yours... that the boys are little NOW, but in the future they won't be. As you point out, boys aren't very likely to shrink -- but they are likely to grow. :-)
You would not NORMALLY say, "Boys now are small"in English. Maybe if you're talking about the size of boys today, compared to their size several hundred years ago, or their possible size several hundred years in the future... but how often would you say or hear that? "The boys are small now" would be a better choice.