what are you objectives in landscaping? Show the overall space in a pic or two.

Beware of landscaping for low maintenance. Over the years, quite a few of my neighbors have replaced their front yard grass with ground covers and shrubs "for lower maintenance". To them, that means a garden service coming twice a year to cut down perennials in spring and fall when they die. They also cut the tall weeds down to ground level (e.g. a large patch of wild goldenrod reached 8 ft before it was cut to the ground.) The original ground covers and perennials are a mess since they're never weeded, and some like Bishops weed and lily of the valley, are taking over. Some areas (e.g. low sedum) are so covered with weeds that the original ground covers are not that visible. The shrubs are overgrown, hanging over the pathways and sidewalk. Overall a very messy look that cost them more money than they would have spent by just hiring a lawn mowing service and keeping their original evergreen shrub foundation bushes. If I were you, I'd concentrate on some hardscape improvements like that hot tub idea and leave much of it as lawn for the children to play on.

I think you should remove any frontal beds (save an isolated shrub or such) and let the groundcover come forward such that it could encapsulate the trunks of all front trees. This would entail the creation of a new bed line, killing a strip of grass at the front of the bed, mulching it, and allowing the groundcover to move/spread forward. There are probably many tall shrubs which you could use to create a screen between yours and the neighboring yards. Look around where you live and see what looks good to you. Then, get it identified. (There is a forum for plant ID. You'd need clear pictures from varying distances, including close up.) If you're interested in hedges that bloom over a long period of summer, look into panicle hydrangeas. There are many that work for hedges.

people incapable of sorting through nuances = HOA boards Looks like your soil is very sandy, so that it could turn out to be murder trying to establish and maintain lawn grasses on the small section of level ground involved with this project - let alone on the sloping part. And since you have a Mediterranean climate July is just about the worst possible time to install a new lawn - wait until later in the season if at all possible. Better yet seriously reconsider having any lawn on that site at all. As for your specific climate area (California has a large number of different climates) and what specific plants might work for your purposes a latter day copy (various editions have come out for decades) of the Sunset Western Garden Book will have such information.