An E-2 spouse is employment-authorized incident to status and may work in the business or elsewhere. Her citizenship does not affect her spouse status, but if she is a Canadian permanent resident rather than a citizen, shares she holds personally do not count toward the fifty percent Canadian ownership.
Spouse status and share ownership are separate questions
The spouse of an E-2 investor receives E-2 dependent status regardless of her own nationality and is treated as employment-authorized by virtue of that status. She can take a role in the contracting business, run its office, or work for an unrelated employer. What she cannot do is contribute to the treaty-nationality calculation unless she is a Canadian citizen.
If the purchase is planned as fifty percent for the applicant and ten percent for his wife, and she holds only permanent residence, the Canadian-national ownership falls to fifty percent, which still meets the threshold but leaves no margin for a later transfer or dilution. Placing the full sixty percent in the applicant's name, or in a company he wholly owns, avoids the issue. Children under 21 receive dependent status and may study but are not work-authorized.
Record each person's actual citizenship documents before the share allocation is drafted.