You don't need to marinate the meat, just throw some pappy's or other rub mix on about 30 min before cooking. Most meats cook a little better if left to sit for a bit.
Ribs are great, but take time. At least a few hours to get a good smoke.
Split chickens take about 40 mins.
Tri tip takes about 90+ minutes for rare.
Party wings about 30 minutes.
Burgers about 20 minutes.
Pork loins also turn out pretty good on the grill. It's been a while but I think its near an hour.
I guess it just depends on how much time you have to devote to cooking and how much effort you want to put into it. I usually have two grills going. One for meats, and the other for sides and sautéed onions, mushrooms, and peppers are always a hit. If I'm doing a long cook, I'll make wings or something as an appetizer while the meat rests.
For that many people though, the lazy man way would be smoking a whole pig overnight. Then they can just dig in right off the grill.