A spouse admitted in E-2 status is employment-authorized incident to status and may work for any employer or run a separate business. Unmarried children under 21 may be admitted as dependants and may attend school, but they cannot work, and their eligibility ends at 21 regardless of how long the parents remain.
A spouse's freedom, and a child's deadline
The spouse's position is unusually generous here and often shapes the household's finances, because it does not tie the second adult to the family business. A spouse can take a job in a hospital, teach, or open something entirely separate. Children are treated differently and the difference has a date on it.
Dependant status ends on the twenty-first birthday, and because this classification offers no direct path to permanent residence, there is nothing for a young adult to inherit by waiting. The realistic options at that point are a student route, an employment route in their own right, or leaving. Families who plan for this in advance often decide which country a child will study in years earlier than they otherwise would, and that decision is easier to make calmly than in the last available month.