Who invited the other 2 couples? Was a "cost" to stay mentioned to them? Many times people who know I go to GREAT places, just think it is a paid for and an extra room where they can stay as MY GUEST would be free to them.
Whenever, ANYONE mentions my travel plans and asks what type of place I am stay, I make SURE they know from my discussion of the condo -- it cost me REAL money and what the costs tend to be. Sure, some friends have ASKED about coming along but they always say upfront, they be willing to pay HALF the costs.
AS for my sibling collection, different rules. I get the unit and THEY buy everything after checking in. FOOD, DRINK, TICKETS, RENTAL CAR, GAS, even a tee-shirt or sun screen ... If several siblings are coming along, I expect they solve the DOLLAR split out of my listening range. AND I do not mention the cost of MFs or how I got THAT unit. I have a great vacation; they seem to enjoy there stay. AND yes, they do cook some very good meals in the unit.
Now, my siblings are employed; if I invite a niece or nephew (under 20yo), I expect to feed them pizza and limit their adventures costing money to what I want to pay. Over 20yo, food in the unit I will cover; all drinks are on them and dinners out are split.