Assume the founder's departure date is the least certain one in the household. Eligible spouses and unmarried children under 21 may seek L-2. A spouse in valid L-2S status is employment authorized incident to status, and an EAD is not universally required; children are not work authorized by L-2.
Sequence the move around the handover
Where the principal's ability to leave depends on successors being ready, avoid committing the whole household to a single date. Discuss whether a spouse's employment plans need certainty earlier than the business can provide it, and whether school enrolment or a lease can tolerate a shift. Petition approval, visa issuance where applicable, admission and permission to work are separate steps, so build the family calendar around the last of them.
Two practical points reduce the risk of a household committing too early. Dependent status generally runs with the principal's, so the calendar built around the worker's approval is also the calendar for every dependant, including any later extension. And a spouse relying on employment authorization incident to status will need whichever document their prospective employer's verification process actually accepts, which is worth confirming with that employer before a start date is agreed.
Hypothetical example: the founder of an animal-feed company plans a January handover, and the household deliberately chooses a school registration deadline that can move twice rather than one that closes in December.