Las Vegas is one of the easiest destinations to organize a larger group around: direct flights from almost everywhere, resort room blocks that scale to any group size, and enough variety (shows, pools, dining, day trips to the Grand Canyon or Hoover Dam) that not everyone in the group has to do the same thing every day.
It also works well as a family destination outside the party-strip perception: several resorts have excellent pools and family suites, and it’s a practical home base for a Grand Canyon day trip.