@Sarah4436 Yes, this can be viable, just be very clear about everything, and do not use Instant Book.
I list a private room in my home in the countryside and while my place isn't quite as unique as yours, it is really only suitable for certain demographics of guests, so I market towards those guests, and it has worked out well. In the first part of my listing description, I say that it's a good place for those who want a quiet tropical vacation, to work on their art, writing, bird watch, practice yoga, or just relax and read their book.
I'm a 20 minute walk to town and the beach in a bustling little tourist town- I don't want guests who like to stay out at the bar, and will stumble home drunk at 1am, waking up all the neighborhood dogs and me.
So describe your listing well, but also speak to the guests who will be a good fit.
And do not sell yourself short- $30 is way too cheap for what you describe. A private place in a beautiful setting is not something you want to advertise at the cost of a shared hostel room, regardless of whether they need to walk a few yards to the bathroom.