The wife, as an E-2 spouse, is employment-authorized incident to status and may run the office or work elsewhere. The daughter may study on derivative status until twenty-one but may not work, and needs her own status after that birthday.
One derivative may work, the other may not, and one of them has a deadline
The spouse of a treaty investor is admitted in E-2 derivative status and, under current policy, holds employment authorization by virtue of that status, so she may manage the office, take an outside job or work for herself without a separate permit, for as long as both spouses remain in valid status. The daughter, as an unmarried child under twenty-one, may also be admitted as a derivative and may attend school or college, but she holds no work authorization; helping on a job site or in the office for pay would be unauthorized employment.
At twenty-one she loses derivative eligibility regardless of the parents' status, and the family should plan now for her to change to a student category or another status of her own before that date. None of the family members needs Canadian nationality; only the investor and the enterprise's ownership are tested for it.