is there anyway for someone to get a visa/green card based on have a child that is a U.S. citizen?

There is no basis upon which someone can immigrate based upon a child who is a US citizen unless that child is 21 years of age. The law allowing babies and children who were born in the US to apply for their parents was abolished in 1976. Your son's grandma can make a visa application explaining the reasons for which she wishes to come to the States and explaining why the visit will be temporary only.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.