Children granted IR2 Visa what now?

[A.m.dcf 3]

Need help regarding citizenship through parent. Here is a link to what I've found so far: https://www.uscis.gov/us-citizenship/citizenship-through-parents

 

I (born a US citizen) petitioned my family through IR1 and IR2 immigrant visas. My wife and her son got an IR1 and IR2 approved and my two biological children got IR2's as well (we are all currently living in the US right now). Now I was under the impression my two biological children would automatically become US citizens upon lawful entry into the United States. The thing is I got a domestic processing fee letter asking for me to pay for their green cards. I already paid for my wife and her son's green card but I've not paid for my own two biological sons' green cards because I thought I could now get them US passports. What do I need to do now to get them US passports as I'm under the impression they don't need green cards. Is there more filing to be done because I was told that others have just applied for their children's passports.

 

Here is the law I'm citing "Section 320 of the Immigration and Nationality Act (INA)":

 

Quote

 

Children of U.S. Citizens Residing in the United States

Children who were born outside the U.S. but now live in the U.S. may acquire citizenship under Section 320 of the Immigration and Nationality Act (INA). A child born outside of the United States automatically becomes a U.S. citizen when all of the following conditions have been met on or after Feb. 27, 2001: 

• The child has at least one parent, including an adoptive parent, who is a U.S. citizen by birth or through naturalization;
• The child is under 18 years of age;
• The child is a lawful permanent resident (LPR); and
• The child is residing in the United States in the legal and physical custody of the U.S. citizen parent.

 

It says my biological children are automatically US citizens. Which implies that they need not file further paperwork. I do however would like to get them passports for travel purposes.

 

Longer version of why my two biological children had to be processed through an immigrant visa is because I did not qualify for the CRBA as I had left the USA to study abroad when I was 15, so I did not have enough time spent in the USA to transfer citizenship.

 

Thank you for reading this and I appreciate any help ya'll might provide.

[aaron2020 11,651]

Upon entry your children's immigration visas will be endorsed and become 1 year green cards (I-551).  Use the I-551 in their passports, their birth certificates showing their age and you as the parent, and your proof of US citizenship to apply for their US passports.  

Edited January 23, 2019 by aaron2020

[A.m.dcf 3]

1 hour ago, aaron2020 said:

Upon entry your children's immigration visas will be endorsed and become 1 year green cards (I-551).  Use the I-551 in their passports, their birth certificates showing their age and you as the parent, and your proof of US citizenship to apply for their US passports.  

When I applied for the CRBA I had paid the fees for passports. Can I still use those receipts to get their passports now more than a year after the CRBA rejection?

Another question is am I required to get the passports now & what happens after the 1 year I-551 expires?

Edited January 23, 2019 by A.m.dcf