It'd have to be done at a place with close access to a shooting range, plenty of space for tables and booths (preferably inside in case it rained that day), and a really big parking area. And it would have to be reasonably close to a large population center, like Lincoln or Omaha. Is there a place with those features maybe between Lincoln and Omaha? If somebody had a range that could be used in that way this would be a good way to make a lot of people aware of it. But I don't know of any such place. I shoot at Izaak Walton outside Lincoln, and I don't think it's big enough for something like that.
It would take a substantial investment in time and money to set it up, and it would be a big gamble, because unless it was all inside, a rainy day could ruin the whole thing. The best way to guarantee a heavy rain storm is to plan an outdoor wedding; this might be the second best way.
I'm guessing manpower could be increased with volunteers, since there are a lot of us who are interested in guns and wouldn't mind spending a few hours doing whatever was needed; there seem to be quite a few NRA certified instructors around, and certified RSOs. Plenty of dealers too, from what I see at gun shows.
This could bring a lot of people interested in guns together and increase membership in NFOA. A big outdoor gun show with access to a shooting range could be a big hit. But it doesn't seem likely to me because of the difficulties.