what I do if it were me?
I would build the submerged board barrier st the fence line then set 18 inch size boulders across the back leaving just enough room to pack a bit of soil in there and put some kind of pretty creeping flox or cascading plants that would cascade over the rocks down the remaining portion of the garden, add a couple of my favorite trees, a garden bench, and flowering perennials.
Just photo shop your ideas... Give your husband's opinion a chance. Give him some alternate ideas. Both of you can sit down together and decide.
Photoshop is just drag and drop on the computer. Pretty basic.
