Just a suggestion, because I am doing this for my daughters next weekends grad party, did it for my own college (late in life) grad party 2 years ago and know many who have done it for all sorts of large gatherings......
A Taco Bar!
Ground beef with the taco seasoning (Sams club for both..Ortega makes a taco seasoning we get there in a big jug and use according to instructions..and we had a bit of salsa to the beef too!)
We get bags of shredded lettuce (no extra work, dump in bowls)
Shredded cheese and we also get big cans of the Nacho cheese to heat in crock pots
Cut tomatoes, cans of sliced olives, cut up onions, big things of sour cream, salsa, and we like the Mrs. Renfros jalapenos. I will aslo do a crock pot of black beans (did refried last time and had a ton left over, but all the black beans were gone fast). No rice for me, but many of my friends do a spanish rice as well.
bags of Doritoes plus we do the little snack bags for "walking tacos" as some of these events are backyard BBQ's
You get the idea. But time and again this has proven to be very economical. We then do some sort of fruit plate (I am doing fruit kabobs with marshmallows for fun at the grad party this weekend), some cookies and bars the lady relatives are donating, then a Root Beer Keg, bottles of water and thats it for us!
Good luck in what you decide, just thought I would offer a tried and true suggestion!