The J-1 Exchange Visitors Visa is for those who intend to participate in an approved program for the purpose of teaching, instructing, conducting research, receiving training, or to receive graduate medical education or training. Nannies/Au pairs and certain Camp counselors fall under this category as well.
Some J-1 nonimmigrants enter the United States specifically to work (as a researcher, nanny, etc.) while others do not. Your spouse and unmarried children under 21 years of age, regardless of nationality, are entitled to J-2 classification. Your spouse and children are entitled to work while in the US.