We were just at Addo, and though we don't have kids, it seemed very family friendly. It is not far from Port Elizabeth, in a nonmalarial area. We stayed in very nice SANparks accommodations; they have a wide range of lodging options. You can self drive or go on game drives with a park guide in an open vehicle. We did both. The kids on our game drives had a blast. We saw tons of animals up close -- many elephants, zebras, buffalo, warthogs, kudu, ostrich, and even some jackals and a hyena. It was quite affordable too.

We also went to a small private game reserve nearby, Schotia Safaris, for an afternoon/evening game drive that includes dinner. This tour lets you see lions (which are hard to see in Addo) and other animals not in Addo and is also well priced. Kids were on those drives too. Addo is by far the more authentic safari experience but this was great fun too, and the combination allowed seeing a wide range of animals without spending a fortune.