First off, I think your recipe sounded yummy! I wouldn't make it for a big group of kids, though, because of the cost. I use real shredded parmesan, not the powdered stuff in the green can, and that costs a fortune. I've never thought to put it in mac & cheese, though. I'm trying that ASAP!
I might make it to serve if one of my DDs had a friend over. I like to make foods they might not eat at home. I have introduced tons of kids to crêpes - lol.
Now, what I'm about to tell you will likely gross you out, but Velveeta doesn't require refrigeration, even after opening. Yes, I'm serious. So you won't see it in anyone's fridge, you'd have to look in the pantry. As for your market, they aren't going to waste expensive refrigeration shelves on something that is shelf stable. Just like the cans of evaporated milk aren't near the fresh milk, the Velveeta is stuck on a shelf someplace, nowhere near the actual cheese. In my store, it's over with the dried pasta and those dreaded green cans of powdered parmesan.