Filling out immigration petition is an easy task for some if they spend time trying to understand the processes. In my past experience, the best source is visa journey dot com. Go to the sub-forums, you will most likely find the instructions in the sticky threads on top. Also, take a good look at http://uscis.gov/greencard web site. You will find all the details and forms there. All USCIS forms come with the instructions to help explain the items in the forms.In short, you will need to submit form I-130 to USCIS with all the required documents and fees. The current fee for form I-130 is $535. USCIS will send a letter to confirm your son's elligibility and a case number will be assigned in F3 category (for Married Sons and Daughters of U.S. Citizens). Keep this paper somewhere safe. If you move, notify USCIS your new address. It will be 12+ years before you hear from USCIS again. When you do, follow USCIS's instructions to complete other forms. His wife and kids will join him as follow to join beneficiaries.A few things to note: your son and daughter in law in their 50 in a new country, the kids will be over 21 years old which make them ineligible to join the same petition.Moving to another country is an important decision. Make sure you and your beneficiaries know and understand all the options.