Huisvrou, for the sake of our fellow forumites, I will respond in English as well, to your questions which I will be able to answer to some extend:
Alternative will be tents and trailer, but it's a small Venter-like luggage trailer, nothing big and camping-ish.
Reaching KTP (Twee Rivieren camp) with a normal trailer is no problem as the road is now tar all the way.
Won't it be very hot for camping in Oct?
I am sure you should still be fine as long as it is early in Oct.
As to the roads in KTP. We travel with a Toyota Fortuner 3D, but not 4x4. It does a diff lock though. Will it be OK for travelling in the park?
On the main park roads you should be fine as long as you avoid the 4x4 trails
What about going Botswana side?
AFAIK, they do not allow you on the Botswana side without a 4x4.
I've seen a lot of mention about the road from Leeuwdril northwards, suppose it will be open in October?
According to feedback I received from them, the road is scheduled to be re-opened end March 2011.
But then Rooiputs were mentioned - I don't see any road via Leeuwdril to Rooiputs on the map of KTP on the web?
There is a road from the Rooiputs waterhole (north of Leeudril) to the Rooiputs camp - I am sure you will be able to negotiate this with your Fortuner if you can do a bit of sand driving and deflate your tyres - which you should in any event do for all the KTP roads - about 1.2 bar.
Anything that I should know, that maybe is different from camping in Kruger?
KTP is in many ways different than the KNP. Take some bottled water with as the water does not taste too good. We normally take our own meat, basic groceries, and some fire wood for at least the first 2 nights as stocks in the shops are sometimes limited and taking some time to replenish due to the distance from Upington. Take some decent tent pegs and a decent heavy hammer as the ground in some camps are quite tough! Blue 3 prong plug and a long extension cord is essential as you will not always find a camping spot close to an electricity point - camping spots are not numbered.
I hope this helps to an extend. I am sure other forumites will contribute more to make your first stay in KTP one that you will never forget.