I second the veggie lasagna recommendation. Here's a nice decadent recipe that even meat-eaters love.
http://www.seriouseats.com/recipes/2012/10/ultra-creamy-spinach-and-mushroom-lasagna-recipe.html

Make a big vegetable stir fry, rice (I often do both brown rice and white rice), then separately, stir fry beef, chicken, and/or shrimp and tofu. Put whatever proteins you decide on on separate plates and the vegetable stir fry in a big bowl. Everyone takes their rice of choice, adds on the vegetable stir fry and then adds their protein of choice. You can do the rice and proteins first and then reheat quickly in the microwave, doesn't take much. Do the vegetable stir fry last (if you prep all the veggies, and put the sauce in a bowl, then it should take you under 10 minutes to put the stir fry together at the last minute). The veggies do better freshly cooked rather than reheated in the microwave (they'll wilt and lose more of their natural texture when cooked more).

Homemade spinach lasagna and salad is my go-to casual meal--you can prep everything before hand and then it just goes in the oven. Serve with apple pie and ice cream for dessert.

I agree with the 10:57 poster -- you can have some cubes of meat & cheese for appetizers, but I think even the most hard-core meat-eaters can deal with one vegetarian meal.

Taco/burrito bar!! Cook up some turkey or ground beef with spices for the carnivores. Cook up some black beans with onions and spices (I also add some tomato paste) for the vegetarians. Lay out tortillas, taco shells, lettuce, tomatoes, shredded cheese, salsa, guacamole, hot sauce, rice with lime and cilantro....etc. etc. etc. Everyone can assemble their own.

And margaritas...of course

Honestly, I think I would look for a really yummy vegetarian dish. This being winter, there are some delicious, filling casseroles that could be cooking in the oven while folks arrive.
If you feel you HAVE to serve some kind of meat, have appetizers that include crackers or small sliced bread with a variety of toppings: sliced meat, cheese, vegetables, tapenade, etc.

Something casual that doesn't require a lot of cooking when folks arrive?

TIA!