If one were translating the Japanese sentence into English with no additional context, then yes, "grandchild" would share the same non-specification of gender that 孫 has.
But considering that this (and most of the sentences) came from the website Tatoeba, the direction of the translations might not be Japanese to English. They could be English to Japanese. They could both be translations from some other language.
You probably figure that out by following the link to the sentences on Tatoeba and reading through the update history, and that would give you a better idea of whether the translation is good or not. But it ultimately wouldn't do much for your ability to change the sentences, because I'm pretty sure only the person who made the sentence can edit it (unless my understanding of Tatoeba has not kept pace with changes to the site.)
In this case the "offending" English sentence was unadopted on Tatoeba, which means I could have changed it.
However since there are other sentences in other languages connected to it I'm hesitant to change the original "grandson" sentence.
Instead I created a new English sentence with "grandchild" and switched it so that one will be used in Jisho and other source that rely on the Tatoeba Japanese index system.
Possible Correction
Should it not be "They spoke well of their grandchild"?