Only the Canadian citizen carries treaty nationality. The enterprise must be at least half owned by treaty nationals, so ownership should be structured around the citizen spouse. The permanent-resident spouse may accompany as an E-2 dependant and is employment-authorized incident to status.
Treaty nationality belongs to a person, not a household
E-2 looks at the nationality of the investor and of the enterprise's owners. Canadian permanent residence is a Canadian immigration status; it is not citizenship and does not make the holder a national of a treaty country. If the permanent-resident spouse holds citizenship of another country that also has a treaty with the United States, that nationality could be used instead, but it must be shown with that country's passport. Otherwise, structure the nursery so the Canadian citizen owns at least fifty percent and holds the developing-and-directing role, and treat the other spouse as the derivative. That spouse, once admitted in E-2 dependant status, is employment-authorized incident to status and can work in the nursery or anywhere else. Children under twenty-one and unmarried may accompany and study but not work. Ownership records, not intentions, will be read, so the operating agreement must match the plan.
Hypothetical example: a Canadian citizen owns sixty percent of a design studio and her spouse, a Canadian permanent resident who is not a citizen, owns the remaining forty percent. The first review checks their passports and the entity records before filing. Residence does not supply treaty nationality, while the ownership record determines the enterprise's nationality. The couple must decide whether the eligible owner's investment and control meet the route's requirements rather than assuming a shared household resolves them.