Legally the dependent applications stand on their own principal's status, so one household's circumstances do not determine the other's. Eligible spouses and unmarried children under 21 may be considered as dependents in each family. Practically, though, the partners should compare timelines, because a business needing both owners present may open with only one household ready.
Agree the cover plan for a partner who arrives late
Decide in advance who carries the operating load if one partner's family is delayed, and whether that changes the profit split for a period. Each spouse's work situation is assessed separately: a qualifying E spouse is generally employment-authorized incident to valid status, verified through the applicable proof, while children gain no such authorization. Record every family member's nationality, relationship, and intended arrival date so both households appear in one schedule.
Add one household matter to that shared schedule: what each family does if only one partner's household can move on time. Beyond who covers the operating load, there are decisions about schooling, housing and a spouse's employment that cannot be reversed cheaply, and two families making them independently against the same uncertain date will make them inconsistently. Agree a common set of stages and a rule about what may be committed at each, then let each household apply that rule to its own circumstances.
Hypothetical example: two partners buying an electronics assembly business agree that neither family gives notice on housing until a defined stage completes for that family, which prevents the more optimistic household from committing on the strength of the other's progress and leaves each free to move at its own pace within an agreed framework.