camtasia is NOT the best solution. You need a microphone if you want to be able to hear it later. Without that, you'll see only the video. Think about that. Getting the right type of microphone is a whole new world.
Depending on machine, camtasia is a CPU hog and it take a bit of time for him to get used to it, file can he huge.
Your best and easiest solution is a video camera.
Good luck.