This is an issue close to my heart as I see my own parents aging; and, having recently finished a project for a lovely 93 year old lady. The best way to make the right changes is to actually walk through the garden with your loved one. Take note of any struggles or obstacles, there may be other obstacles than what I have noted.
The first and easiest is to keep paths clear, do not leave anything on their path that does not belong. Our elders rely on memory to move through a space and if something is out of place, they may not see it. Their reaction time will be delayed. Steps can become a challenge, but taking them out may not be feasible. Also, they are used to those steps, their height, etc… Consider adding a sturdy metal handrail. The thickness of the rail needs to be small enough that their hand can grip it well. Make sure the rail starts and ends parallel to the ground; it must also extend about 8″. That 8″ is important so that there is plenty of room to complete the change in elevation. Does water puddle anywhere? That can lead to slippery mold, so make sure that is addressed. (Possibly drill a hole so water can drain) Another important step is to look closely at any breaks in concrete or loose paving material. Also any change in a level path. Gravel, unless compacted, may not be a good material….especially if it is rough. One more thought, consider placing chairs throughout their route, preferably in a restful spot, so they can rest.
It is important to encourage our loved ones to get out of the house and into the garden for some fresh air and to commune with nature. Taking a few steps can really help them feel comfortable doing that, and hopefully will give you some peace of mind.
Great question! Feel free to submit a question my advice.