Do I file a DS-260 form or an I-485 form for my EB-5 application if my kids are already studying in the U.S.?

If the children are in lawful status in the United States when they are eligible to file to adjust status, one would apply for adjustment of status, rather than consular processing.

In order to file the I-485, the principal must be eligible to adjust and all the derivatives. If the principal or any of the derivatives are abroad, they have to file the DS-260 forms.

The way I would have done it would be for you to proceed first through the consulate (DS-260). Once you arrive, they can do I-485 applications.

If you are the principal, then the case is adjudicated at the next stage at the location you indicated on the I-526. If you are in legal status and in the U.S. when the I-526 is approved, you may all file I-485s.

In order to file I-485 for dependents who are in the U.S., the principal has to obtain IV and enter the U.S. The kids can then file I-485s. Note that, at this time, I-485s based on I-526 take 2+ years to adjudicate.

If your children are in the United States in valid nonimmigrant status and you wish them to apply for adjustment of status, do not file the DS-260 forms for them. If you plan on them traveling to Chile and applying with you or after you for their immigrant visas, then you should file DS-260s for them. If any of them are close to the age of 21, you should file DS-260s as soon as possible.

If you, as the principal applicant, are currently residing outside the U.S., then you should file DS-260. Your children can file DS-260 and consular process with you in Chile, or they can file I-485 after you become a conditional resident.

If the children are in the USA, you can file the I-485s here.