Yes. E-2 spouses are employment-authorized incident to status and may work for any employer, for themselves or in the family business. Children may study but not work, including in the family business, and lose E-2 dependant status at 21 or on marriage.
Spouse's work is unrestricted; children's is prohibited
The spouse of an E-2 principal is authorized to work by virtue of E-2 dependant status, without a separate application, and the annotated admission record serves as evidence for an employer. The spouse's employment need not relate to the enterprise: a Sainte-Brigitte-de-Laval investor's partner who is a dental hygienist may take a clinic position, subject to state licensing, while the investor runs the business. Children under 21 may attend school at any level but may not work; a teenager who helps on job sites or in the office of the family company is working without authorization, which can affect the whole family's status.
Dependant status ends at 21 or on marriage. Because E-2 does not lead to permanent residence, no immigrant petition protects a child who ages out, and a household with a child in late adolescence should plan the transition to a student classification or a return to Canada from the outset.