Here's what we ended up doing:
We bought too much! It stretched further than we thought. So I'll give numbers for what we used here.
We bought 5"x4" trays from Amazon. They are the hot dog trays that are white with red stripes. We put 7-8 chips in each.
For the cheese sauce, we added 1/4 gallon milk per can of nacho cheese sauce. I would recommend starting the sauce 1 1/2 to 2 hours before service. Heat it gently on medium heat stirring often if using a big pot. Or for smaller pots you can start earlier. We mixed it in a big pot and then transferred it to a smaller pot to heat it faster and get it to the roaster. We ended up burning the bottom of the big pot though because we turned the heat up too high.
What we actually went through:
24 lb. of chips
4 cans of nacho cheese sauce
1 gallon of milk
500 nacho trays (we didn't use them all)
Not everyone took nachos. We also had toppings, but they're optional. I would probably skip them next time.
1 gallon salsa (we had 1/2 gallon left)
1 #10 can olives (we had 1/2 can left)
1 #10 can jalapenos (we had 1/2 can left)
Cheese & Crackers.
We bought 1200 Ritz crackers (2 boxes from Costco), one whole slicing ham, and 4 packages of cheese (32 slices per package). They preferred the provolone over cheddar, so next time I would do 3 provolone to 1 cheddar. This time we did 2 of each.
We sliced the cheese into 9 pieces per slice. We used a meat slicer to create thick slices of ham and then cut them up into cracker sized pieces. It created 1600 slices so we could just use the nice inside pieces. It was the right amount. We had maybe 150 left (not counting the extra ham).
Mini Cinnamon Rolls
My friend is a master of cinnamon rolls. She made us almost 1000 mini cinnamon rolls in mini muffin pans. We had about 150 left over.
I used the toll house recipe on this web site. I made a triple batch 4 times. I used a tiny cookie scoop leveled off to make almost 600 cookies. They were all eaten 2.5 hours into it.
We made these on site as we went. I baked the brownies in mini muffin pans, 48 per box. That was a mistake. They were hard to get out. The kids loved them and we couldn't keep them stocked. But next time I would do two boxes to one jelly roll pan and cut them into small squares. I would probably add more brownies as well, and do 8 or 10 boxes. We only did 6. They went fast.
Our Restaurant Supply Store sells Restaurant Mints like Starlight Mints in 5 lb. bags. I got 1 bag of each flavor (cinnamon, starlight, & chocolate. We put them in huge vases that the kids could reach into. They were a hit! We went through almost all of them.
We did 3 water dispensers with just water. We were on a carpeted floor that had just been cleaned and we didn't want sugary drinks. In one we put lemons. In another we put cucumbers, and another was just plain water. We went through 40 lb. of ice within about an hour. We needed much more ice! Fortunately the water was cold from the tap.
We brought 2000 cups and had a few hundred left over. We provided sharpies for anyone that wanted to label their cup. I don't think that many people saved their cups though.
We served it all as finger food. We gave them no plates other than the box for their nachos. We gave them napkins. We brought 1200 napkins but only used about 350. The food wasn't very messy or sticky.
We heated the nacho cheese on the stove and then poured it into a roaster to keep warm. The roaster held 4 cans of nacho cheese plus a gallon of milk worth of cheese sauce. That's all we needed for the night. We had kids with a ladle pouring the cheese with self serve condiments to the side.
We picked up some trays and bowls from the dollar store. We loaded them in the kitchen and then swapped them out when they got low. We were constantly swapping trays but it was better than hovering around the table trying to refill them from the back.
3-8' tables were used so the food was spread out over a large area. That was necessary as we still had bottlenecks of kids trying to access the food table. Most of the time it was enough space.
One table had the water. The middle table held the treats & crackers. The end table held the nachos.
As far as helpers went we had 6 adults and a few teens helping us out. I would recommend 10 people minimum. It was exhausting work.
We mostly ran pitchers of water to the dispensers all night and swapped out trays of food. The hardest part was hauling everything in and then back out. Make sure you have extra people for that.