One thing to keep in mind is whom you are feeding. If it's mostly your son's friends, and if they're like most young men and are furnaces that burn up food as fast as they can wolf it down, you'll need more food. If there are as many old folks and little kids, who tend to eat about half of what active adults eat, then it'll balance out. Rule of thumb for entertaining is generally 1/2 - 3/4 pounds, uncooked, no bones, per person, but you're making unitary foods that can be cut in half, but generally go one hot dog or one hamburger at a time. Unless they're particularly small, you'd probably be fine with one hotdog or hamburger per child, 3 per teen or young adult, 2 per active adult, 1 per dieting woman or old folks who've heat the eat less phase. Always figure an extra package or two (depending on size of package) of each to cover miscounts, extra guests, fallen in the dirt, and the one who brings the dog and feeds it people food.

For salads and sides, most adults will take a scoop of everything. Dieting women/girls might skip some of the dips and chips. The guests who run hungry, like the young men, will either go for seconds on the most popular stuff, or just fill up another plate or two. Children are pickier and you can generally count them as half an adult. It's hard to know which of the sides and dips and all they will or won't eat if you don't know them well. If there are 2-3 generous portions left of everything before the teens who are hungry again lose patience and clean out the bowls, you've had enough. The trick is to try for that amount, plus whatever overs you might have brought just in case. It's a big trick!

Figuring drinks is harder. Will they be playing baseball or picnic games? Or is this more of a sit down thing? Is it shady or sunny? Will it be hot? No matter what, it's a good idea to bring plenty of water if there aren't good water fountains at the venue.

You didn't mention vegetables except cole slaw. You know your crowd. Do you think they might be missed?