wow...Kilimanjaro...I barely know where to begin. Well, I guess with the boot question: I hiked Kili with Vasque Sundowner MX2 GTX boots with Vibram soles and found that I really needed the ankle support of this higher boot. The boot has a Gore-tex lining, and I re-waterproofed my boots with Nikwax two times in the two weeks before I left for Tanzania. I had already been hiking in those boots for over two years, so they were very well broken in. Broken in boots are key, and it is important to pack them in your carry-on on the plane because everything but your well broken in boots is replaceable in Tanzania.
I also have the same Merrell low boots that Sli74 has, but I use them more for summer day hikes. Since all I had to carry on each of the eight days we were on the mountain was a day pack with water, camera, food, extra layers, etc. which totaled around 10-15 lbs. (the porters carried everything else), I suppose low boots would be fine as long as you had trained in them in the mountains over rugged terrain and felt comfortable with the support they provided.
Other key gear--tall gaiters, 0 degree sleeping bag, headlamp with lots of extra batteries, down/synthetic jacket for warmth in camps above 12,000 ft. or so when it starts to get very cold at night, ... there is so much more I could say, but this is a good start I think. It was the most incredible trip of my lifetime!!!!