Your ownership percentage does not decide that. A legally married spouse admitted in qualifying E-2 dependent status is generally employment-authorized incident to that status. Confirm it with the person's own I-94 or E-2S evidence, not with residence or payroll arrangements. Unmarried children under 21 may accompany but receive no work authorization.
Verify permission before starting work
Visa validity is relevant to seeking entry, while the I-94 generally records the authorized stay after admission. Do not simply use whichever date is shorter. Check the spouse's documents, basis for work authorization, and effects of the principal case on derivative status. An offer may be conditional; actually starting work requires valid authorization.
Children lose dependent eligibility at twenty-one, which for a family that arrives with a teenager will happen during the assignment rather than after it. A child qualifies as a dependant while unmarried and under twenty-one; there is no discretion in the age and no extension of it for a child still in education. Children under 21 may study at any level but may not work, including in the family business; a teenager helping at the counter is unauthorized employment.
Purchasing or owning equipment does not authorize anyone to operate it in the United States.