Just to agree with nbaresjr, renting the 18-300 seems like a waste. You wouldn't be getting any better images than your kit lens, likely lower quality. Simply more reach.
Better off renting the 17-55/2.8, which will give you vastly better image quality. And if you feel you need the additional reach at times, also rent something like the 70-300, though you'd probably only need it for the safari.
"All in One" lenses sacrifice image quality, weight, and low light ability, all just to achieve an all-in-one convenient range.