@Terri426
A possible idea
Another host with a beach property had two listings for her property. Active for either peak season or off peak, She mention peak season she priced as you for full capacity but off peak season she priced 2, 4 or 6 guests so two was the basic and then price adjustments after that so she wasn't limited to only the larger groups during off peak.
I would suggest also you change your focus for off peak. When I was in Hawaii, we would have to help people see that there is a lot to enjoy if it is raining your week and that sort of ruins the beach ideas. Focus your pictures your ad description maybe on bike trails since there are bikes, sights in town besides the beach or in Hawaii they had horse back riding on the beach. Tourist spots have off peak fun but you have to help build that imagination for guests.