Satara is my favourite camp, and I was due to stay 8 nights there as part of 26 nights in the park in 2 weeks time, until the announcement yesterday :-(

Satara is situated in a fantastic area, in the middle of KNP. One night, my personal opinion is not enough, I would have done a minimum of 2.
There are some fantastic roads nearby, and really wide open spaces, with (quite often) many big cats around.

The H6 is a super road, and the 'famous' S100, which is a dirt road known for lion sightings is also good, but I prefer the H6, always lucky on that road.

Satara are also currently having a new deck built for the restaurant, which has just been taken over by 'Cattle Baron' the restaurant which is also at the Skukuza camp.

Lower Sabie is also a decent camp, and 2 nights is fine. It can get busy down south, as game is usually plentiful betwen L.Sabie and Skukuza, so if you do see a 'traffic jam', I would advise you simply do a u turn. It's a shame you couldn't do 3 nights Shinzela and 2 at Satara, you would have probably got more out of your itinerary.

Small auto car is fine. I always take an auto, and have driven a Polo before, but now always take the Toyota Corolla. Have had a Ford ecosport and a Rav4 as free upgrades, didn't like the Ford Ecosport, but the Rav4 was nice. Everyone usually says a high vehicle is better, but to be honest, when I take pics, I prefer slightly lower down, makes for better photos The difference in height isn't that big a deal to be honest. No problems with the dirt roads either with small sized cars, plenty of folk drive them in the park.

Happy to provide any info via PM is you need any more info.