But I need some advice: For the high school graduation of one of my sons, I am looking for an Camera. He likes to photograph birds and planes, and now landscape at climbing.
Sounds like the 7D would be a great camera for him - great AF system for birds and motion, super fast continuous frame rate, APS-C sensor to give more "reach" to the lenses. Perhaps with a 70-300mm if zooming in close is always the priority. Or perhaps the 70-200mm f/4 IS for more "general" use beyond just birds and planes, (or the 70-200mm f/2.8 II IS version if he is a super serious photographer). You could wait for the 7DII if he really needs "more camera" than the 7D offers, but who knows when that will actually come out.
Regarding the buffer issues, as mentioned turn off the High ISO Noise Reduction feature, and make sure you are shooting only RAW and not RAW+JPEG, turn off Peripheral Illumination Correction, and perhaps even turn off Auto Lighting Optimizer and Highlight Tone Priority.