With the amount of time you have and the desire to include Kings Canyon in your trip plans, I think the better choice would be to fly into Alice Springs and out of Uluru (or vice versa depending on flight schedules). We did this once and it worked out quite well.
If there's a huge drop-off fee for the one-way car rental, then you could certainly fly in/out of Uluru, but I don't think driving to Kings Canyon and back for a 1 night stay there would be my first choice.
If you go to Kings Canyon, a 4WD is best so that you can go via the Mereenie Loop. It saves a big backtrack via Curtin Springs. You'd also need to get a permit (just a few $$) at Kings Canyon gas station or Alice Springs Tourist Info Center.
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