How can I doctor up a 6 pound can of nacho cheese to make it taste a little better and more presentable? Desperate in the kitchen

What about adding a can or two (or three) of mild green or Hatch chiles to the cheese?

Wow, what a large amount!
As the cheese sauce is a kind of universal element most people will add to their nachos, I would not change it a lot.
For visual appeal, maybe have several stations with the cheese in fondue pots or other attractive ceramic pots over heating elements.
Possibly garnish simply with chopped cilantro, grape or cherry tomatoes, or dust with cayenne or ancho dried pepper.
For taste, maybe boost with the white queso or some cheddar.
Also, there are many ideas online of what to include in a nachos bar...cooked beans and/or meat, raw veg, salsas, chilies.
Beers with lime wedges. Tequila, plain or mixed.
Good luck and I hope it's all lovely and tasty!