You have a lot of meat for 70 people, which will probably decrease the amount of pasta you need. 1 pound dry penne makes almost 8 cups cooked. For 70 people, for generous portions, do about 15 pounds pasta.

Penne Vodka Sauce for 70-
Big servings, 15 pounds pasta about 1 quart sauce per pound. Does not reheat very well; best made day of. Hold or reheat over very low heat.

10 tablespoons olive oil
10 onions, chopped
garlic is actually optional, but if you use it, about 1/4 to 1/2 cup whole peeled cloves, crushed
10 28 ounce cans crushed tomatoes (that is 2 #10 cans; skim off any seeds you can)
1/4 cup fresh or 1 tablespoon dried oregano
70 -90 fresh basil leaves, chopped or 3-4 tablespoons dried basil leaves (use the fresh, please)
2 tablespoons salt
1- 1 1/2 tablespoons fresh ground pepper
5 cups butter, divided
9 pounds fresh white mushrooms, quartered, about 30 cups
1 teaspoon crushed red pepper flakes (to taste)
5 1/2 cups vodka
5 quarts heavy cream (half and half only if you must, it affects the thickness)

6 tablespoons kosher salt
15 lbs rigatoni pasta penne
3 cups dry parmesan cheese, plus additional for the table (additional, 1 ounce per person, 4-5 pounds)

Start the water boiling, it will take almost 1/2 hour to get to a full rolling boil. You need 16-20 quarts water, you could do 2 pans.

Heat the oil in a large saucepan; when hot, saute the onions (and garlic if used) until golden, about 5 minutes. Add crushed tomatoes to the saucepan. Stir in the oregano, basil, salt and pepper and simmer 1 hour to concentrate flavors.

While the sauce is cooking, heat half of the butter in a skillet over medium heat. Saute the mushrooms and hot pepper flakes until the mushrooms are golden. Some people like to add prosciutto here, about 1/2-1 ounce per person

Carefully add the vodka to the mushroom mix and simmer for 5 minutes to cook off the alcohol.

Add the heavy cream to the mushroom mix and bring just to a simmer; pour the cream mixture into the tomato puree; stir to mix. Keep the sauce warm while cooking the pasta.

Add the kosher salt to water. Bring to a rolling boil. Add pasta to boiling water; cook uncovered until pasta is al dente, about 12 minutes. Drain well.

Now, DON'T skip this step! Melt the remaining butter in a large skillet. Stir into the drained pasta to glaze, then add Parmesan cheese and mix thoroughly.

This is the optimum service:
Stir in 1/3 of the sauce and mix with the pasta; divide among plates. Top each plate with some additional sauce; pass remaining sauce and additional cheese at the table.

If you must serve from a chafer, stir in 2/3 of the sauce and have the last third in a crock pot or warmer for gguests to add extra.

Here are 2 not quite from scratch vodka sauce recipes:

Soup base
www.campbellfoodservice.com/recipe.aspx?RecipeId=759

This one uses a jar sauce as a base:
www.conagrafoodservice.com/recipes/recipe_view.jsp?action=recipe&recipeid=5583&view=view