We’ve done three big trips with extended family (one trip was smaller than the others and we booked two 2 bed villas, the other two trips we booked a studio and two 2 beds). We had 13 people on the smaller trip and 17 on the larger ones - all aunts, uncles, cousins. We basically offer up the idea of the trip as an invite to all 18-24 months in advance and provide an estimate of what the ticket costs and plane tickets would likely be. Basically the invite is that we’ll provide x number of nights of accommodation if people want to come and here is a guess of what your other expenses might be. We usually split the cost of a grocery delivery and usually we are treated to dinner one of the nights we go out though that is not at all an expectation we have.
We do ask people to commit to coming by a certain date so as not to be stuck with reservations we don’t need but our extended family is also especially close and in each other’s business and no one would ever flake on us at the last minute barring an actual emergency. I think you really have to understand and accept the dynamics of the people you are inviting and plan accordingly or things can go south.
