His wife, as an E-2 spouse, is employment-authorized incident to status and may work in the business or elsewhere. Children under twenty-one in E-2 dependant status may study but cannot work, including seasonal shifts in the family's own garden centre.
The family payroll is where investors trip
Family-run retail businesses assume everyone helps out, and that assumption is the mistake. The E-2 spouse's position is good: her work authorization is incident to her status, she may take a salary from the enterprise, run the design studio or work for another employer, and she may also be counted in the business plan. The children's position is different.
A seventeen-year-old stocking plants on Saturdays is working without authorization, whether or not she is paid, and that exposure can affect her later applications. Plan staffing so that the seasonal labour comes from US hires, which also strengthens the non-marginality case. Each child loses dependant status at twenty-one and will need student or other status then.
Note also that the family's nationality matters for the principal only; a spouse who is not Canadian may still be an E-2 dependant. Since E-2 has no direct path to permanent residence, a family expecting to stay indefinitely should discuss long-term options at the outset rather than after several renewals.