We're just back yesterday from a wonderful holiday in SA.
We stayed in Cape Town, which is a lovely city, but the beach is poor. A couple of miles down the coast is Camps Bay, which is a beautiful resort with bars, shops and a lovely beach with a large tidal pool. BUT, the sea is freezing all year round (Atlantic). The slightly warmer sea round the coast is generally unsuitable for swimming because of the sharks.
We did a safari on a game reserve about 2 1/2 hours out of Cape Town called Aguilla. It had gorgeous 'hunting lodge' bungalows to stay in, a really nice pool, restaurant, shop and bar etc. There were quite a few children staying there (under5's I would say) who were enjoying the pool and the animals which came in close to the bungalows. We did a game drive of around 3 hours and I also did a horseback safari of a couple of hours. We saw elephants, lions (very, very close up), rhino, hippo, springbok, wildebeest, zebra etc. Although there were no children on our jeep, there were on others.
Another place you might like to see is Boulders Bay - there are hundreds of penguins on the beach, and you can get up close to them on boardwalks, we really enjoyed that.
Any questions I can help with, do ask.