As you might well has suspected this has nothing to do with choosing a camcorder and everything to do with audio recording. Microphone placement and/or taking feeds from the sounddesk and mixing are the areas you should be looking at. It maybe that you end up with a mixed feed going to the mic input of your camera or you may end up with a recording on another device which you mix with the cameras's footage later. The best camera/mic combination will not give you even barely acceptable audio if you are moving around whilst recording. The sound needs to be recorded from a static positions. The sound on the camera is used only for syncing up the separately recorded sound.