"Whose children are these, yours?"
Translation:Чьи это дети, ваши?
We say "это" if we want to know whose are some children. WHOSE is stressed. Like in general questions: что это? кто это? чьи это?
We say "эти" if we want to stress THESE: Those are mine and whose are these? Те - мои, а чьи эти?
So, both pronouns can be used, depending on what do you really want to know.
I've had this question about word order too. From everything I understand, it's acceptable. Every time I check the comments, the reasons people post for it being wrong make no sense. The only one that makes sense to me, which no one has said, is that it's one of those weird things about Russian that just doesn't make sense and has to be this particular way (english has a bunch of those, so I could understand that).
So, until someone can give me a valid reason for it being wrong or I stumble across the rule myself, I'm reporting it and telling duo my answer should have been accepted.
I'm guessing that you have progressed to a point where you won't need this, but it's here just in case you took a break from study or for others to access ))) Have a wonderful day http://www.russianlessons.net/grammar/pronouns.php