She may work: an L-2 spouse is employment-authorized incident to status and does not need a separate sponsor. Whether she may practise physiotherapy is a state licensing question, decided by the state board, and it is entirely separate from her immigration status.
Two clocks run at once for the accompanying spouse
Treat the licence as the long pole and start it first. Hypothetical example: a specialist transferring from a Saint-Cyrille-de-Wendover panel plant to an affiliate in Tennessee expects his wife, a physiotherapist practising in Quebec, to begin at a clinic soon after arrival; her L-2 status permits employment from the day she is admitted, but the state board requires credential verification, an examination and an application, and the clinic cannot employ her as a physiotherapist until that is done. Physiotherapist does appear in the USMCA Appendix 2 list, so a separate professional route may exist for her, but it would require its own offer and its own qualification evidence and it is not automatically the faster path.
The children’s position is simpler: unmarried children under 21 accompany as derivatives and may attend school. Note the interaction with this classification’s five-year ceiling — a child who is sixteen when you start will be twenty-one before an assignment reaches its limit.