You have a beautiful awesome home. You might want to limb up your trees. By that I mean raise the canopy of some of your tree's closer to the house for colorful plants. Or just thinning a tree's branches. Don't cut them down. Work with it. I'm not in your climate but Azaleas & Rhododendrons shrubs should work. Also use all of the fern family's. Impatience's annuals love shade as do perennial Hosta's in all family's I would consider working in some very large rocks in to the terrain near the entrance for more interest & making them look like natural. Also check into moss gardens, they can be beautiful and there are many moss colors. A good green house can do soil test for you and buy high shade plants then per their advice. Sometimes it's not the shade but the soil that needs improvement even for shade loving shrubs & plants.

Thanks Kevin.