Mexican food is my favorite way to feed a crowd. Pork Carnita Tacos are great and can be down in a slow cooker if needed.

Seconded, but maybe mix it up with Korean tacos: http://www.gourmet.com/food/2009/05/korean-tacos

Nobody will turn down guacamole and margaritas. Make a side of beans..
Gourmet Magazine in one of its last issues did a gorgeous Mexican taco platter. Can't find it but it was absolutely beautiful, and easy for a crowd. I am continuing to look.

Mexican food is a great idea - a build-your-own taco bar with a protein in the slow cooker and all the toppings stashed in the fridge til you're ready? Or maybe curry/chicken tikka massala in the slow cooker with a big pot of rice?
Or if you're really fatigued, order pizza! You've got a two-year-old, so everyone will understand. :)

These Hearty Italian Sandwiches work well as a make ahead and always are a hit. I use mild sausage and substitute yellow pepper for the green--serve with a slice of provolone and dill pickle. Also should mention 6 hours in a modern crockpot is too long! I usually just do it in the oven until the veggies are tender and then transfer over to a crockpot to keep warm if I'm serving a group.

http://www.tasteofhome.com/Recipes/Hearty-Italian-Sandwiches

Corrected link for Pork Carnitas, oops!

I second the Pork Carnitas idea! It is super easy to keep warm and everything can be made in advance.

I like braising meat for a crowd. You can do it a day in advance and it tastes better because the flavors meld. I posted a recipe for Braised Turkey Legs for the Holidays, I hope it helps!
http://www.soireesandsuch.com/wp-admin/post.php?post=180&action=edit&message=1

sorry, wrong link http://www.soireesandsuch.com/2011/11/28/braised-turkey-legs-in-red-wine-sauce/

I make either a couple kinds of chili or tacos for about 60 college girls once a year--they're the easiest things to make, I think! (And homemade refried beans that aren't actually refried, just left in the crockpot...delicious)

Dumplings! It's not entirely make-ahead since I like to boil them and that needs to be done right before, but it only takes a couple of minutes in boiling water before they are ready. You can also do a dumpling-making session beforehand, which is a fun activity for those interested. Or, make way ahead of time and freeze individually. Serve with rice and have everyone make their own sauce (I always put out soy sauce, sesame oil, chile oil, Chinese "BBQ" sauce, black vinegar, and Sriracha). As a variation, you can do hot pot, if you have a couple of camp stoves or something similar to put on the tables. Prep all the ingredients ahead of time, then everyone has fun throwing in fish balls and veggies!

I forgot all about this until the mention of feeding the 60 college girls, but when we were feeding groups of college students I'd often cook up turkey in advance and shred it to serve on buns with barbeque sauce on the side.

The night before Thanksgiving (this year), I threw a Mexican themed bash. I made carnitas, chicken, and chipotle beef tacos. I made the carnitas most of the way the day before, and just had to throw it in the broiler right before the party. The chicken was also made the day before, and the beef was started in the crockpot that morning. I kept the tortillas warm in a cooler (it works!). Everything was awesome!

I would definitely do it again. I had very little day-of work to do.

The recipes I used:

Carnitas - http://www.seriouseats.com/2010/07/the-food-lab-how-to-make-crisp-and-juicy-carnitas-without-a-bucket-of-lard.html

Chicken - http://www.seriouseats.com/recipes/2011/06/shredded-chicken-and-tomatillo-tacos-queso-recipe.html

Beef - I put cubed chuck in the crockpot with a sliced onion. Added a big can of crushed tomatoes and a few chipotle peppers in adobo that I whizzed up in the blender. Also a bay leaf.