The household composition matters more than attendance. Establish which spouse and which unmarried children under 21 would join, because each of them must be considered in the initial application and each adds US$15,000 and US$1,000,000. Deciding that list early changes the budget conversation entirely and may change whether the household proceeds at all.
Discuss each person's own position
Ask the reviewer to look at every intended applicant individually, not just the principal. Each person's immigration history and admissibility matter, and a difficulty affecting one family member is better found now than after payment. Where an adult child, a partner not legally married, or a relative outside the described categories is involved, ask specifically how the program treats them rather than assuming.
Record the answers so the household can weigh them together afterwards. Ask specifically about anyone whose position is unusual, because those are the cases where an assumption is most expensive. An adult child, a partner who is not legally married, a stepchild, a child approaching twenty-one, or a family member with their own immigration history each deserve an individual answer rather than an inference from the general description.
Record the answers in writing so the household can weigh them together afterwards, and remember that each person who does join is considered in the initial application and carries their own charges, so the list is a budget decision as much as a family one.