Hi @Maricar102
What a fantastic property!
Technically, once a reservation begins, the Guest cannot change the number of guests on the reservation. Several points were made here that the guest should notify you if someone is not able to make it BEFORE the reservation begins; not after. The primary renter should go to those that didn't show up and ask them to reimburse the primary renter since they didn't make it for the trip. That said, it's up to you as to whether you want to refund them for the 2 persons who didn't show up:
Changing Number of Guests on a Reservation
https://www.airbnb.com/help/article/913
Cover Photo
Your place is so great! Might I suggest a change to your photos; especially the cover photo? Research shows that collage photos (4 photos in one) don't do very well as a cover photo on Airbnb. This is because the thumbnail is so small and guests can't see the detail very well when it's crammed into the space for one photo. Any photo with water does very well. Try this for your cover photo for now and see what happens?
I would use the following as your next 4 photos, as they show that not only can you enjoy peaceful solitude at your place, there are plenty of activities for groups. Color contrast between the photos is also important (the photos shouldn't be all the same basic colors, but contrast with each other). Research also shows it is better to depict people enjoying the space(s) instead of just interior shots of rooms. You have some great photos of that. Try these as your next 4 photos after the cover photo:
Photo 2
Photo 3
Photo 4
Photo 5
Let us know here if you notice any increase in bookings with these photos. Give it a month or so. If no change then switch up the photos again. 😊