Thanks Gardengal, I will keep that in mind.

Anything you buy will have to be watered at first, to keep it alive until it roots out well. Since watering is a hassle with your project there try planting right before heavy fall rains start, this may not be until November - cold hardy drought tolerant selections like junipers planted at this time might just be able to start establishing well enough before the following summer to squeak by. But you will still have to monitor the situation, be prepared to water as needed at least that first summer after planting.

Mulching soon after planting will probably also be critical to success. Covering the soil with organic mulch or cobbles, so that the summer sun does not quickly bake the moisture out of the upper part often makes a big difference to results gotten from plantings.

Dogs like to pee on anything of any height present along access routes and in other prominent situations. Also junipers with depressed centers such as Pfitzers I have seen multiple times with dog piles nested in them. So if it is at all possible to get some kind of low fencing installed around the planted islands that could be worthwhile. This might also serve to help reduce damage from children and vehicles.

As mentioned anything installed will probably have to stay above - as with a tree with an elevated crown - or below eye level for safety reasons. And if this is a situation regulated by a body such as a municipality or neighborhood association there may be rules that have to be followed, restrictions on what is allowed.

Rather an unusual choice but there are certain cold hardy varieties of pomegranate that can survive (particularly Russian ones). They are very drought tolerant, although will be late to leaf out in the year since they like warm weather.

Taiwan raspberry is another low maintenance one (more like an ornamental low ground cover than regular raspberry plants, and they deal better with the heat in the summer).

The latter is not tall enough to suppress weeds of any height and is armed with prickles which can make weeding torture without adequate hand protection.

Hardly prickles....they really just have some bristly stems. I've weeded a patch before without any issue. It is also one of the best weed suppressing groundcovers I know of, so weeding is seldom an issue with an established planting.