You need 1 pound per 4 people, 10 pounds.
If I were doing a long cooking sauce, I would cook several meats in it; meatballs, ribs, braciole or round steak, chicken. This would add variety without being more work for you.
When doing a potluck with unknown brings, you want to do the meat or entree, which you are already doing, one green salad, bread, and one half of dessert- in your case 2 9x14 dump cakes or cobblers.
Take a look at the spaghetti dinner for 50-60 at the bottom of the spaghetti page and do about two thirds.