I also like your itinerary, and you have a good mix of different camps already. Between Mala Mala and Londolozi I prefer Londolozi but overall the experience will be similar. They both have a huge area of prime land and the game viewing will be about the same. The differences are in the way they do things, the level of experience of their rangers, and to some extent the accommodation (depending on which camp you go to, both Londo and Mala have multiple different camps).
Elephant Plains is fantastic value for money and I would not swop this out for another camp.
I also like the sandmans suggestion of adding more to your time inside the Kruger National Park. Kruger itself is a different experience to what you get at the private game lodges, and in my experience the overall game viewing is better in Kruger. You will cover a lot more distance, and see greater numbers and variety of animals in Kruger.
The ability to self-drive in Kruger is one of the things that makes this park so popular. Alternatively, if you want to experience something a little different from what you already have on your itinerary, you can consider a guided open vehicle safari in Kruger itself, if you want the benefit of an open safari vehicle and an experienced guide.
I think you will have a great trip!
Onne from Wild Wings Safaris