Assess the spouse’s status and work independently. A qualifying L spouse may work incident to valid dependent status with appropriate evidence, such as the applicable spouse-specific I-94.
Keep corporate convenience separate from individual permission
A related company’s willingness to pay does not create authorization, and the principal’s approval does not automatically grant the spouse status. Qualifying unmarried children under 21 may accompany in L dependent status, but do not receive the spouse’s work benefit. Answer the spouse's question in its own order, and do not let the company's convenience set that order.
First, does the spouse hold valid L dependent status? Second, can employment authorisation incident to that status be evidenced, commonly through the appropriate spouse-specific I-94? Third, and only then, what work is being proposed and by whom is it paid?
Hypothetical example: a related company offers the spouse paid bookkeeping for the group on the basis that the family is already relocating and the work is familiar. Willingness to pay creates no permission, the principal's approval extends none, and doing the work before the status question is settled is the risk that is hardest to unwind afterwards. Unmarried children under twenty-one may accompany in L dependent status; that status carries no equivalent employment benefit, and it ends on its own terms as the child ages, which is worth diarising rather than discovering.