Ask your family what they would like to see, not designwise, but plant materialwise - color, texture, fragrance. Even ask your mother-in-law. You have provided some architect's dream, with the bold geometric forms, the bold palms and cycads. How about something warm and fuzzy. Something to rub your hands on as you head to the door. Some color and fragrance beyond the white and palm trunks. How about vines to soften the hard edges of the planters, fill them with ground cover plants so you won't see the mulch in a couple years, add bulbs of all seasons to bring cheer, glossy leaves to brighten your day. Bring nature to your entrance area to warm up the arrival of your mother-in-law. How about saving room for a couple chairs and small table, to sit out and prove that people actually live in this piece of marvelous sculpture, and add the warmth of an outdoor room. Spend some time at the library with books about the architecture of Frank Lloyd Wright. He is the one who introduced the architectural design idea of the outdoor room. Come to think of it, I don't remember ever seeing a garage door in any of the photos. Guess I'll have to take another look.

Houzz, this needs moving to design dilemmas.

coming from a northern country to Australia, I miss the white Christmases. A white decorated theme makes me feel at home and brings back happy memories whilst experiencing a non-traditional hot Christmas.

Your site is far too exposed for Maples. They are small trees that really need to be buffered from winds and too much sun by other plantings. They also need the soil constantly moist which will be nearly impossible on that slope. You really don't want to grow magnolias anywhere near the footings of a house. Have you seen how large a tree they are? Since you are in a temperate zone and like autumn foliage I can recommend a gingko tree. It will be right sized for your yard and give you that similar lighter than air look and autumn colour as maples but it's more hardy. Another option are silver birches. I would hedge the boundary for privacy and also to cut down winds to your garden which will dry out the grass and scorch it. With that slope you are going to need more rocks I think to prevent your topsoil from washing away in the first rain. It's really no use of us to provide you a list of random plants. What you need to do is put together a series of photo's of gardens you like the look of, then find plants to match that style. If you don't plan gardens then you end up with the ubiquitous suburban patch of grass and odd bushes look instead of a lovely garden.