You'll want to avoid the "hunt, skin, chow" lion potjie option as it has been reported that 90% of the Kruger lions have feline aids (know where that comes from?).
I'd advise you to book if you want to stay in the park, especially this month. At peak times they even want you to book for day trips into the park. Two nights is a bit short - you definitely won't be able to do north and south in two days and see anything worthwhile. My favourite camps are Punda, Letaba and Lower Sabie (although it looks as though the character of Lower Sabie has changed since it was rebuilt).
Here are some pics taken in the winter of 2007. I stayed at Ngwenya and made day trips into the park. I must admit I wasn't too impressed with Ngwenya though.