Another pasta idea that's quite good at room temp, so I often take it to potlucks, is to steam or grill some asparagus and maybe a few red peppers, cut into pieces the same size as penne pasta and toss with warm penne, olive oil, salt, pepper and generous handfuls of grated parmesan.

Another way would be to use fresh baby spinach leaves and cherry tomatoes instead of the asparagus/red peppers...No cooking except for the pasta! Comes off as a pasta salad.

Perhaps too late, but in this thread I suggested an Egyptian dish called koshary:

http://www.food52.com/foodpickle/3172-i-am-cooking-dinner-for-30

Amazingly cheap to produce, vegetarian, so good for a mixed crowd, and despite it's humble origins, it's just exotic enough to be interesting, yet familiar enough that even fussy kids will eat it. One of the few vegetarian entrees I do which does not leave me thinking that it was good, but would have been better with a bit of pork...

The ham, pasta and cheese sounds fabulous. I don't have a favorite, but I'd just do a great bechamel with lots of minced onion and thyme, and a bit of decent, sharp cheddar. And I'd put some whole grain croutons on top with some parmesan, butter and a tiny bit more cheddar. So the whole thing wouldn't be too cheesy, sloppy, gooey. I'd add mustard to the bechamel, too. I'm totally with you on finding something other than oranges for the salad, but I do like the fruit idea, a lot. One of the easy apple + celery salads would be perfect. I really like the Harvest Apple Salad, which would be kind of colorful with the butternut squash. And don't tell me you're lazy. Anyone making lunch for 25 tomorrow is not lazy. Sounds like a great lunch. Wish I could be there! ;o)

Sheesh! That sure is last minute!!

Oranges and thin sliced red onion are great together. You can make a big platter of that. Just peel the oranges all around and cut into 1/2 inch slices. Scatter onion slices over. Top with the nuts. Arrange chopped romaine around the perimeter. Drizzle of vinaigrette over the whole thing.

Nothing wrong with a giant ham on the table. Put a bunch of sides with it - mashed potatoes, or roasted potatoes, some green beans or broccoli.

Don't forget a big basket of bread. Butter on the side. Or get rolls or biscuits so people can make a ham sandwich if they want.