I have a green card; my daughters are 18 & 7 years old with vistors visa. Can they go back and forth until their green card arrives,

Your daughters may encounter some difficulties in doing this as they are supposed to only have nonimmigrant intent, and staying the majority of the time in the US while only going back for short stays overseas could raise flags with Customs and Border Protection (CBP). There is a good chance, however, that CBP officers may overlook the situation in light of the sympathetic circumstances. Due to the limitations of the Lawyers.com Forums, Alan Lee, Esq.'s (the "Firm") participation in responding to questions posted herein does not constitute legal advice, nor legal representation of the person or entity posting a question. No Attorney/Client relationship is or shall be construed to be created hereby. The information provided herein by the Firm is general, and requires that the poster obtain specific legal advice from an attorney. The poster shall not rely upon the information provided herein as legal advice nor as the basis for making any decisions of legal consequence.