Try the area on the east coast south of Mozambique and north of Durban.
The beachs and wildlife are superb.I stayed in St Lucia and also visited Sodwana and Hluhluwe-Imfolozi gamepark
Try the website below for other info.
I am a mid aged english guy and have travelled all around SA and would recommend the area for at least a weeks stay .
Forget the garden route in my humble opinion and enjoy all there is to do in Cape Town and Stellanbosch with the time saved on travelling.
Good luck, SA is a marvellous experience for all ages !!!
I'll leave the Cape Town bit to the local experts we have on here, but I'm a big safari fan.
I've just come back from three superb lodges - Kings Camp, Leopard Hills and Madikwe Hills. My reports are posted on here for them so take a look.
Little Madikwe can be booked out just for your familiy and you get your own ranger and cook too! It's a two bedroomed suite so ideal for a family - i saw it when I was there and it's mind blowing! And it's malaria free in the Madikwe.
The game viewing is better imo in the Kruger however so try Kings or Leopard Hills and get two suites - they are gorgeous.
Have a great time.