pama2024

Thank you everyone, you've all been truly awesome! A special shoutout to @Dashinka , @Crazy Cat and everyone involved. The suggestion to start the application process six months in advance is brilliant. We are likely to take that route. Thanks again to all of you.

The children should be able to get derivative visas from whatever her current visa status is, so they can move over at any time. But to stay longer term, as said above, you'll need to petition for them - just as you'll need to petition for her if she wants to stay in the US. 

Is your GF on a J-1 w/ a 2 year home requirement? You shouldn't make any plans yet until you have this answer.

Tend to Agree.  Some ideas to consider.  Anyone else have thoughts?
 
OP can marry, then:
1.  File an I-130 for each of them.
2. Spouse can file an I-485 to adjust status.
3.  Children can do consular processing in home country.
This could cause issues for spouse due to travel/work restrictions after filing I-485
 
Option 2 after marriage
1.  File an I-130 for each of them.
2. Spouse and children all do consular processing in home country (Spouse travels back to home country for medical & interview).
This is going to take quite a bit of coordination and travel. 
 
Thoughts or ideas, anyone? 

It is just we know very little of the situation of your girlfriend and her children.  Does she have sole legal custody of the children?  Is their father still in the picture?  You have to look at situations like this when bringing children to the U.S. as if the father is still in the picture, he will need to grant some level of agreement to allow the children to immigrate.  You don’t need that to actually file an I130 for them, but it will be needed at the consulate interviews if they are required to have one.
 
Good Luck!
 
P.S.  I would suggest pursuing an I130 over a K1 here.