ghom is unspecific as to whether the subject is ghaH (he, she), 'oH (it), or chaH (they) -- so using chaH in a sentence on its own is clearer. But if the context makes it clear that you are speaking about several people, then ghom on its own can be sufficient, without a subject pronoun.
Not necessarily. With -chuq, they would clearly be meeting each other, which is the most likely interpretation of that English sentence. But both that Klingon sentence and that English sentence, in the right context could also be used to mean something like, "they hold meetings in the great Hall."
However I noticed that the reverse translation was not accepting -chuq so I have added it now.