I need a quick dinner to feed 12 people tonight without a lot of sides.

Pasta dishes won't need a lot of sides. Carbonara is quick, easy and delicious. Or just go with a meat sauce, with garlic bread and green salad. Meat pies is another option: chicken pot pie or shepherd's meat.

Burritos are an easy make ahead, especially if you make them "mission style" http://food52.com/blog/7267-how-to-make-any-burrito-in-5-steps
The filling is up to you. Have bowls of guacamole and homemade salsa on the side. Chips and maybe a Mexican style slaw.

Make your own taco bar. All you have to do is cook up meat, shred so chicken and have all the toppings out.

Some good, big crowd foods I turn to are: lasagna; chili; roasted chickens. Big salad goes with all and some good bread.