I find that Kenco Rich tastes almost if not better than ground coffee. Keep a new jar unopened until the event and when you open it there will be the lovely aroma of rich coffee.
Nescafé Alta Rica is IMO far and away better than most instants. I've known people who are very sniffy about instant to grudgingly say that it's pretty good. Personally I prefer it to Azero.
I find the Kenco millicano instant (and other "barista" style instant coffees) taste better than some cheap filter coffees and nearly always use them. I've never had Nespresso so can't compare. Everyone has different tastes in coffee anyway. Not everyone will want coffee, some may want tea or soft drink.
I'd stick with Nespresso or filter - out of 40 guests not many will want coffee in my experience. I've been served Azero and it tastes the same as any other instant.
At one time most guests would have coffee but now the majority say that they can't have coffee after 14.00 or they'll be awake all night.
I'm doing a family lunch next month for 40+ of DH's rellies. (I foolishly mentioned that he only saw his cousins at funerals) We only use filter or Nespresso but for large numbers this won't be on. I've seen Nescafe Azero recommended by Which? but would prefer real opinion.