Before you think about going out of the U.S. to get your green card, you had better find out whether you are subject to the unlawful presence bars to returning to the U.S. If so, are you eligible for a hardship waiver? Your U.S. citizen children do not have to accompany you if you do decide to abroad for an immigrant visa abroad.
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I would agree that you seek the services of an immigration lawyer to discuss and assess your case before you leave the USA.
There may be information that will assist you in making an informed decision in your case.