I've used the camera in such situations (personal family snaps, a couple dinner events, etc) and here's what happens: the first couple times people will notice and give you a look. Thereafter, if they see you preparing to take the photo, they have become more comfortable in front of the camera, and will probably pose. If they don't see you, they won't pose and probably won't be interrupted but by now are comfortable and won't really care.
Bottom line: it may draw attention if people aren't expecting it. If they are expecting the camera, then it won't matter at all. Under ideal circumstances, you could rent the camera, under slightly less idea circumstances you could test it out at a camera shop, and under even less ideal circumstances maybe you could find someone in your area, and under least circumstances, buy a used one with a good return policy to see how it works. *shrug*
Again, the AF and motor drive are the loud parts. It'll probably sound louder to you, since it's right next to your face, and the sound does diminish as it gets further from you. But overall the whole thing is quieter than my srt101 shutter (the only "loud" shutter I have). The camera noise is so consistent with a typical camera noise, that I think after a few shots, people will become comfortable with it.
The only thing I might say to be caustious about would be if your noise-sensitive areas are also low light. The G2 sometimes works in low light for me, sometimes not, and confirmation of focus in these situations may be tricky. Again, I think the best way to determine all this is to find a way to test drive it...
What I can do for you: try to record the sounds compared to an M2 and Zeiss Ikon and canonet ql17 gIII. I know this will be relative to the volume of your speakers and distance I hold the microphone from the camera.
