I believe that most interviews are for to make sure that your family can surivive
as new immigrants. So you will be talking as if you are doing a job interview with
an HR manager, friendly, open, fluent, smart and easy to be understood by westerners.
The goal is to be liked, not necessarily to be impressed. Meaning don't stretch
anything or yourselves.
Many years ago, I was almost announced dead. The interviewer was very hostile and
for some reasons, disliked me (us) in the beginning. Luckily, my English was very
impressive and I believe my talk served as a persuasive presentation.
My wife didn't talk any English (but another Euro lingo), I told the interviewer
that in fact she doesn't really want to go, but very affirmatively said that I
wanted to go and I would make it.
It was very much like a miracle when we eventually received our landing paper.