Build the schedule around the dependent with the longest path, usually whoever needs a consular appointment, since appointment availability varies by post and is not something the family controls. Visa exempt children can be ready quickly, but that does not accelerate anyone else.
Sequence around the slowest step
Start by identifying which dependents need an appointment and check availability at the relevant post before fixing a move date, a school start, or the end of a lease. If a child is approaching 21, raise that with counsel early, because the timing of the family's steps may matter more for that child than for the others. Responsibility for the schedule cannot be handed to its fastest-moving part.
List every dependent's step beside the party that controls it: the consular post controls appointment availability, a registry controls how quickly a certificate is issued, an inspecting officer controls admission on the day, and the employer controls the start date. The family controls only the order in which it asks. Fix nothing irreversible, whether a lease ending, a school registration or a resignation date, until the steps controlled by others carry a realistic date.
Hypothetical example: an irrigation-systems designer holds back the resignation letter until the child who needs a consular appointment has one, and treats every other date as provisional until then.