Maintaining Green Card Status

[yogkul]

Hi,

We got Green Card in August 2011, while I was in USA and my Family (wife and Son) in India.
I recently entered USA on green Card, till then I was on H1B.

My family is India since India May 2011.

My family is planning to relocate to USA in April/May of this year (2012) , will there be any issue on entry ? Is there any documentation we need to complete to maintain their Green Card ?

Appreciate your response.

Thanks
Yogkul