"It is a traditional family."
Translation:Είναι μία παραδοσιακή οικογένεια.
I guess you could say "Είναι μία οικογένεια παραδοσιακή", but it would be just a bit weird if you don't mean to give any emphasis, because it sounds emphatic. ^.^
"είναι παραδοσιακή οικογένεια" is currently marked as incorrect, general strengthening on web.
Ghost sentence. Not sure how you keep on bumping into these, but you do :P You are right though. Μία is not necessary. ^.^