One nice thing about living in Northern Wisconsin, you can securely cover and protect your huge sandwich smorgasbord and use your garage as a refrigerator. Another suggestion, find something as big as your serving tray, fill it with ice and it should keep everything cold.

Not unless you have a huge fridge! You have to make ahead what you can (leave out), but add refrigerated foods (like set the salad out, or add the meat and cheese) right before serving!