We self drove through Hluhluwe in a rented toyota carolla. We got a flat tire on the dirt roads. The paved road that runs the park is better, but also full of potholes.
I don't recommend a self-drive through there. We also drove from Richard's Bay to our lodge, back to Durban and several side excursions, our only issue was in Hluhluwe.
You shouldn't have a problem with that route at all, especially if you are driving a hilux. It means you get to see more of the park. Not sure how long it will take as the speed limit is restricted once you are in the park but not more than a few hours.
We were up there a few weeks back and they are working on a maintenance programme for the roads. They had definitely improved in some areas.
It shouldn't take more than 2 hours to get from Richards Bay to the park gate. From the gate to Hilltop will probably be another 2 hours depending on your route and how much you stop to look at game, possibly more.
Hello and why choose the Cengini gate unless you just want to drive the length of the park? The Nyalazi Gate is a good entry point but that will mean tar all the way to Hilltop. As said allow at least two hours as it wil take that keeping to the speed limit with no stops. I have self driven the park may may times and its a stunning location!
Mark - Owner - SafariKZN