US Immigration from Venezuela

Hi, I am filling out the I-129f form to bring my fiancee from Venezuela here. She has two children. I have entered the children's names on the I-129f form. I would like it if they could travel with her. I assume the consular officer needs to approve the "bona fides" of our marriage first. Assuming that happens, what do i need to file for her children? I found this line in the I-129f processing guideline "Note: The US Citizen may also apply to bring the K-1 Visa holder's unmarried children, who are under age 21, to the United States." How do I apply? what forms do i need to fill out? I have read in other places that I need to fill out K2 visas for each child? What exactly are the steps, e.g.:

1. submit I-129f form

2. interview in Bogota

3. K-1 visa approved

4. At this point, how do I get her 2 children into the country? What do I need to do? Will the consular officer in Bogota stamp the kids' passports?

Many thanks for any and all information!