What a wonderful birthday experience your mother is in for!

I am a 67 year old woman and will be travelling with my 69 year old brother to South Africa this February.

I have been 3 times, for about 3 months each trip. Have travelled with another person for the first month, then solo on each trip. I have driven the Panorama route once and the Garden Route twice and spent many weeks in Kruger Park and Addo Elephant Park, visited a couple of other national parks and spent time in the Western Cape.

My brother has never been to Africa, and while I would love to show him everything, I believe that for us, seeing less, and travelling at a more leisurely pace will make for a better experience. We are both excited about animal sightings, and wine, and we enjoy road trips so we plan to divide our time between Kruger National Park and the Cape Winelands with day trips in our rental cars. I will share my thoughts and our rough plan in hopes that it might be useful.

Our rough plan:
We have not made bookings yet, but here is our rough plan:
Arrive Johannesburg and drive to Kruger, spending the first night outside the park, near one of the park entrances.
Spend about 8 nights inside the southern part of the park self driving and perhaps taking one or more of the 2 hour guided safaris out of the rest camps that you can book with Sanparks.
Drive back to Johannesburg and fly to Cape Town.
Divide our nights between Cape Town and Stellenbosch, with day long road trips.

Kruger:
In my experience you will see the most in the southern part of the park. Skukuza, Lower Sabie, Satara and Crocodile Bridge rest camps. We will likely book 2 nights in each.
I love spending hours watching herds of elephants interact, and getting early morning sightings of big cats, so I prefer self driving. Getting up before dawn and being at the rest camp gates (with my morning coffee) when they open has paid off with many amazing viewings. ( That said.. no guarantees!) Driving for a couple of hours in the early morning then returning to camp or stopping at another rest camp for breakfast works well.

Cape:
From Stellenbosch we will self drive to some of the wine farms, (taking turns being designated driver), and take Uber to others.
From Cape Town we will do day long road trips to visit beaches, see penguins and visit other attractions.

Hope this is a little helpful. I am sure that whatever you plan you will have a wonderful experience!