What about Tanzania??? Amazing. We went to Rufiji River Camp in the Selous National Park last year and it was not a disappointment. It's very intimate and natural. We flew by light aircraft from Dar es Salaam to get there. It's not like some of the huge ones on the Masai Mara where it's just crawling with jeeps or the ones in South Africa where the animals are almost tame. I know I'm generalising but I'd be dissappointed if I ended up in one of these places. Of course that's a personal opinion. Some people just want to see the animals no matter what the set up is like. At Rufiji it's so peacefull. YOu stay in tents which have concrete floors and en suite facilities. There are proper beds with mosquito nets which are sprayed every night. The staff are wonderful and are so discreet as all Tanzanians seem to be. At night, because it is very dark, you are escorted back to your tent by a MAsai warrier. They are often employed as security guards as they need very little sleep and they are brave. One night an elephant was eating from the tree right beside our tent. When the elephant moved on I heard the Masai appear from where he was watching it an follow it discreetly to wherever it was going.
At Rufiji they take you out on boat safari where you see wonderful birds, loads of hippo, water buffalo (if you're lucky like we were), crocodiles etc. On land we saw the usual suspects. I don't think they have Rhino there and we didn't see leopard but in real life you're extremely lucky to see a leopard. We did see a lion though and I was so emotional when I saw it.
http://www.rufijirivercamp.com/
The guy who owns it (Luigi) has been in Tanzania since the 1970s so I'll bet your Dad would like him. He's usually proping up the bar drinking coffee and smoking. You'd never gues that he was the owner, he's cool. It's also quite a small intimate site so you can talk to other guests if you feel like it. From there we went to Zanzibar and spent a few days in Stone Town and then a week in a beach resort. Stone town is amazing. YOu could also spend a day or two in Dar es Salaam as we did. It's worth seeing and your Dad may get something fromt that part of the trip too.
We booked the whole trip through Trailfinders. They were great.
I wouldn't take him to South Africa as that couldn't be further from the old Rhodesia that he left all those years ago. I think Malawi would also be lovely as would Mozambique. They are still very authentic. Get onto Trailfinders to start with and take it from there.