For 80 people, I would think of this less as a “private jet” request and more as a group charter / airliner charter problem.

A typical business jet is not the right tool at that passenger count. You would likely be looking at an ACMI/charter broker that can source a regional jet or narrowbody, then coordinate airport slots, handling, passenger manifest, luggage, catering, and Spanish/European charter rules. For Barcelona to Ibiza, also compare whether a block of scheduled commercial seats plus private ground/VIP handling solves the actual problem more cleanly; the flight time is short, so boarding logistics may matter more than cabin luxury.

If they still want a private charter experience, ask brokers very specifically: aircraft type and seat count, operator/AOC, total price including taxes/handling, baggage limits, departure airport/terminal, cancellation terms, and what happens if the aircraft changes. At 80 passengers, vague “private jet” quotes are where people can get surprised.