When I cook for large groups (I've cooked for as much as 75), I make large double batches and then I make multiple entree types. Agree that even if you make more than one type of chili, that you should consider something else as well, whether a sandwich platter, a mac-n-cheese (homemade mac-n-cheese is always a favorite and really easy), a stew, soup (great autumn meal component), etc.
Here's my favorite non-beef chili recipe and it's VERY popular. A few tips: definitely do chicken thighs. I've made it with chicken breasts to be healthier and it wasn't nearly as good. I use poblano peppers instead of green peppers. Canned tomatillos work fine for this recipe. And the most important rule for good chili is to use good quality chili pepper (McCormick or other chili pepper from the regular supermarket pales beside good chili pepper). This is the best chili pepper out there:
http://thechileshop.com/dixonmediumhotredchilepowder.aspx I know that it's too late to order for next weekend's party, but keep this in mind for the future.
The chili recipe:
http://www.epicurious.com/recipes/food/views/Chicken-Chili-Verde-3012#ixzz0qqvt363P