Abit confused about benefits..

[general]

Hi

I apologize if this has been answered before but my situation is a little complicated.

My wife and son were granted there visas and are now here in the uk. What i wanted to know was I am claiming working family tax credit and child tax credits for three of my children who are BC's and child benefit, can I claim child benefit for my son who has joined me and family tax credit for the wife.
I have read that child benefit is not considered a public fund and working families tax credit for immigration purposes. I don't want to have problems when applying for indefinite leave to remain.

Also as regards to Nhs will the wife and my son have to pay for medical treatment?

Thanks