Good question. You might try posting in the gardenweb forum on Houzz instead of "design dilemma". In my area, many people hire out the lawn mowing and edging jobs, typically every two weeks, and care for the flower beds themselves.

Lovely garden! As someone who is getting near that "seniority" myself, I am planning my next garden accordingly.

I do not know where you live, what climate you have but nevertheless I would like to share a few plant names which have survived, even thrived after an unusually cold winter (-6 C's at nights for a week) in a very hot and extremely dry Mediterranean region, with twice a week watering and once or twice a year manure & compost feeding: strelitzia regina (Bird of Paradise), society garlic, Agave attenuata, yucca gloriosa, agapanthus, flax lily (dianella tasmanica), pony tail palm (nolina), cycas and last but not least if you like them daffodils, gladiolus', freezias' are most energy/labour efficient, they do not require much dead heading or drop leaves, no pruning, not invasive and mostly disease/parasite free and they are ever green except the bulbs.

All of the above mentioned plants do like semi-shade and survive sun in our climate.

Since the design question is a matter of taste I do not wish to comment on it. Yet, looking at the photos you have provided I would humbly suggest you to consider to slightly raise the beds along the edges for your back and knees sake and consider minimizing the lawn by replacing most of it with a choice of your stone or concrete slabs with low maintenance grass or creepers in between them.

"Replacing" grass with slabs does not necessarily mean to hire a professional to dig up the whole garden, make a mess for days & bring extra cost: You can do it yourselves gradually by, buying the choice of your slabs in sizes you can carry on your own and start laying them over the existing grass. First start as if you are planning a path of stepping stones from the house towards the garden and sleep on it for while, than add more as you like, where you like it.

Raising the beds: Also the same way, you can do it yourselves by doing it gradually. Pick your choice of a material such as wooden stakes/logs or stones to make dry walls of 30 cm's in height or more if you wish.

I hope I have been able to help even if slightly... enjoy your lovely garden!

Check out the books by Piet Oudolf. His focus is on prairie plantings, which include native plants, i.e. milkweed, purple coneflowers, liatris, asters, etc. They are low-maintenance - no need to spray them for diseases and they attract tons of pollinators. Just go on the Internet and do a search for prairie plants and design. Youtube also is a great resource. Lastly, make sure to add ornamental grasses, for texture and movement in the garden. I don't cut down any of my prairie plants down come Winter - I garden in Zone 5, Illinois. The plants provide a great source of food for the small birds and they also add a beautiful texture to the Winter garden.

When I bought my current house, I hired a landscape designer to create a “5 year plan” for my yard. Her fee was reasonable, and it was great to have her roadmap to follow as I implemented my low-maintenance yard (some sections alone, some with the help of installers). It was a very collaborative and enjoyable process, too.

Thank you for bringing up this question, Marsellen (sorry, can't get rid of cap). Where I live (Saskatchewan), -6 is warm in the winter so I need hardy plants. I, too, love my home and a nice garden, but am "getting on". I don't mind mowing, although sometimes I do it over a few days and sometimes hire it out. Weeding is an issue for me, though, so I bought a "kneeler" so that I can get up after getting down to plant or weed (arthritic knee). I love hostas, hydrangeas, day lilies. Am going to look into some of the plants suggested above and try for some hard scale and mounding as well. I have taken to using potted plants (annuals mostly but not all) on my deck. They need a bit more hand watering but that becomes a pleasant task in the late afternoon as it cools down. Interested in hearing other ideas and what prairie grasses survive colder climates.