Partial attendance
Not everyone can travel the whole time. Capture who is in for which stretch instead of pretending the roster is fixed.
A week in June is not a Friday night. Some people can only do the first half. One budget is a hostel, another is a rental car. School, work, and flight length sit in the way. Get those constraints onto one brief before anyone pays a deposit.

These are not weekend problems. They are why a longer holiday stalls if you jump straight to an itinerary.
Not everyone can travel the whole time. Capture who is in for which stretch instead of pretending the roster is fixed.
May half-term versus a cheaper June week. Compare windows, then close one. The date planner is for the calendar; the brief is for what those dates have to survive.
One person wants hiking. One wants rest. One wants a city. Priorities belong on the brief so the destination argument has a reason.
A range per person, not one number that nobody actually agreed to.
Flights, weather, and how far people will go. A shortlist with votes beats a locked city that half the group cannot afford.
School holidays, work, maximum flight length, passports. Put them next to the dates, not in a side thread.
The longer start adds attendance, priorities, and constraints on top of when, vibe, where, and budget. That is the same who β when β vibe β where β budget model, with the extra layers a week-plus trip actually needs.
Friends can answer from the shared link without creating an account. If you only need Friday to Sunday, use the weekend planner instead.

Agreement before the itinerary.
ShorterWhen the trip is two nights, not two weeks.
StepsThe sequence from start to overlap.
On the webWhat the browser can do while people answer.
After the briefIdeas and a shared plan once the constraints are visible.
WindowsCompare the date ranges, then carry one forward.
Far enough that school, work, and flights can still move. For a week or more, start the brief months out so date ranges and who can come for which stretch are visible before deposits.
Collect a range per person, not one fake group number. Stays and destinations can then be compared against what people actually offered, instead of discovering the gap after a booking.
Treat partial attendance as a first-class fact. Note who joins for which stretch, then pick dates and a route that can absorb late arrivals instead of forcing a full-trip roster.
Start a bigger trip on the web, share the link, and see who can actually come.