We have a few friends that come up with their 3 or 4 kids in tow every year on various weekends, and other weekends a couple of my adult nieces and nephews come for a day visit, usually during the summer.
We take them out on the boat for the afternoon; bring drinks, fruit, and snacks for everyone on board, then go back home and I fire up the grill while my wife sets everything else up.
I grill a couple of big London Broils (top round steaks sliced thinly for serving with a steak sauce or au jus), hot dogs, chicken legs, sweet onions, peppers, and stuffed, giant portabella caps.
The day before, my wife makes macaroni salad and /or baked ziti, a giant salad, garlic bread, and appy plates of chips, nuts, cheeses, salumi, and chips/crisps.
We've never said anything to anyone about the cost (marine fuel, food costs, anount of time prepping, then cleaning up - both the boat and house after the fact, etc.) or proper manners or anything, but everyone seems to show up with a small dessert and enough alcohol for them to consume themselves.
At least one of the families invites us to their house for a pot-luck New Years Eve party every year.
The way I look at it, providence has been in my favor, so I'm just passing it along.