Thanks very much for your reply Wei Shu and for the other who replied. The answers provided are very helpfull for me.
My 3 children are australian citizens . they are not included in the application.
** are you sure about the entry requirement, because my wife should get the permenant residency straight away without needing to wait 2 years under provisional visa subclass 309?
** we are applying from UAE(Dubai). Visas there are easier usually to australia, do you have any idea how long does it take to get the visa?