Its only a week, how much do you honestly think you will use? Plus, shouldn't the condo come with things like toilet paper? We camp every summer, usually 4 day trips at a time. Before each trip I stop off at the dollar store and get paper plates, tin foil, cups, and paper towels. Maybe two of each to get you through 7 days? I can see Costco if you were spending a month there, but not a week. A small dollar store thing of laundry detergent would probably suffice too. You are on vacation. How much laundry do you realistically think you will do while there? Swim suits and towels should be hung to dry in between uses and can be laundered when you get home.ETA_I missed the siblings part! Oops. How many people are we talking about here? That would factor into my decision on Costco or not. So would the question of whether or not they will be bringing some too.