I used to live on Big Island and still visit often (I have lots of friends and distant family there) - I’ve used Knutson & Associates in the past for condo rentals and was very happy with their service and the rentals - I see they have some homes on their listings - Kona Hawaii House Rentals | Knutson & Associates
As an alternative they have several condos at Keauhou Kona Surf & Racquet Club (where I stayed when I rented with them) - you might like 2 or 3 units which would give far more space, and lots of bathrooms for a large group - maybe pick one that has a great ocean view lanai and enjoy evening meals together there.