Yes, they will have to apply for immigrant visas abroad but that process is much longer and more onerous than I-485. Why did you not file I-485 for them concurrently? They'd have their green cards within 4-6 months of filing. And if they were not unlawfully present in the US prior to the I-485 filing, they would qualify for an advance parole travel document to travel while I-485 is pending.
Answered on Apr 09th, 2014 at 11:53 AM