Either can work depending on the household's own circumstances, but the decision should follow the applicant's confirmed entry rather than precede it. A spouse or children would travel under a dependent status without independent work authorization for the spouse.
Decide staging based on confirmed status, not hope
If the applicant's admission goes smoothly, the family can follow soon after with less uncertainty about the underlying case. If questions arise at the point of entry, a family that has not yet committed to travel avoids added complication. Discuss with the household what a short delay would mean practically, and keep dependent documentation ready regardless of the chosen stage.
Decide the staging from the applicant's confirmed status rather than from the household's preference. If admission goes smoothly the family can follow soon afterwards with far less uncertainty; if questions arise at entry, a family that has not yet travelled avoids compounding the problem. Discuss at home what a delay of a few weeks would mean practically, and keep each dependant's documentation ready regardless of which sequence is chosen.
A spouse or child would travel in a dependent status carrying no independent work authorisation for the spouse, so any employment plan a spouse holds needs its own assessment on its own facts rather than being folded into the principal's case. Agree the sequence in writing.