For loyalty events: less is more. A group of 20 to 80 guests works best. That's big enough for atmosphere and variety in conversations. And small enough for personal contact with every guest.
The guest list is a strategic choice. Invite the people you absolutely don't want to lose: your most loyal clients, your longest-running partners, your most important stakeholders. The sense of exclusivity reinforces the appreciation.
Read more on the ideal setup in our article on organising loyalty events.