TSC, if you sort the night before you can have it pretty much sorted. These are my least faffy buffet suggestions.
Cook a massive thing of pasta, stir in most of a jar of basil pesto and a packet of pine nuts. Then get one of those huge bags of cocktail sausages and cook them. Make a dressing with two table spoons of honey to one of wholegrain mustard and half a tsp of worcester sauce, and toss the sausages in it (you might need to make a double amount for a lot of sausages)
Buy a sheet of puff pastry, spread with a mixture of 2tbsp ketchup and 2tbsp English mustard. Sprinkle with grated cheese and cut the pastry into two long strips. Roll each strip lengthways and cut slices off so you have lots of little spirals. Bake and serve warm.
For coleslaw mix 2tbsp sour cream, 2tbsp mayo, 2tap lemon juice and some black pepper. Stir in 1 large onion, 2lg carrots and half a white cabbage, all shredded.
Those are a few fail safes, I can give you more if you need them too.