Let’s start with the bad news (sorry): quite simply, no camcorder on earth is going to do the job you want, even half decently unless you invest in the audio system. By this, I mean neither an internal mic or any single shotgun mic mounted on the camera. You need proper audio kit for this job.
Why? Well firstly, no intermal mic on any camcorder is going to cope. Internal mics are good only for recording ambient sound (birds chirrping, traffic, etc etc) and even then only when the quality is not critical. They would be hopeless at recording a voice from within a group of 100 people unless the speaker bellowed. Further, no single mic mounted on the camera (like a shotgun mic you see on TV news cameras) is going to work much better either.
To sensibly and decently record someone speaking into an internal or shotgun mic, they need to be within 3 feet or so of it. For the internal mic they’d also need to project their voice and be in a quiet location. Both options mean you shadowing the chairman with the camcorder like a wasp buzzing round a jam sandwich.
Then, assuming you want the audience responses picked up as well, you’d have to run from standing next to the chairman to point the camera up the audience’s nose too and hope they didn’t speak before you get there.
Now, if you want to record the chairman clearly and if he’s not going to move off a fixed point then you could either wire a tie-clip mic to him or put a shotgun mic on a stand in front of him. Any solution wired in to your camera also prevents you moving much either though.
If he IS going to move, you’ll have to invest in a wireless mic and lapel mic for him – by far the best option.
For the audience, a separate solution is required. Usually this would be done by one or more dedicated boom operators (holding a long pole over the audiences’ heads and pointing a shotgun mic on the end towards whoever is speaking).
Alternatively, the audience members can be instructed not to speak until a handheld radio mic is handed to them. This would be picked up by one of two receivers (one for the audience mic, one for the chairman), perhaps played out over a PA system – not so loud as to cause feedback of course.
Audience members are not the best people to handle microphones however, as they tend to have zero grasp of mic etiquette and will either ‘pop’ by speaking too close to them or wave the mic around aimlessly instead of holding it steadily pointing at their mouth. A trained boom operator is the much better solution.
The problem for you then is to take those two feeds and combine them into your camcorder. Actually, this is not so complex. You need a camcorder with a microphone socket (ideally a line-level socket but mic level will do) which can take the feed from the radio mic receivers / PA system. This may involve some cables and cheap converters eg to end in a 3.5mm jack that would go into the camcorder. Pay particular attention to the levels or the sound could be badly distorted.
Thus the chairman’s mic can be recorded on the left channel and the audience’s mic recorded on the right channel (these can be panned to centre in an edit afterwards)
I realise that this is a substantially more complex solution than you may have been looking for. Unfortunately, simply buying a new camcorder will not do the job you’re after, even with an external mic mounted on top. Audio is one of the most complex things to get right especially in the scenario you describe.
The only way you might get away with a mic in or on the camera is if the audio was going to be PA’d as described above and you stood next to a loudspeaker so that you were recording what came out of that. It won’t be pretty but it might do the job. Possibly.
Either way, the chairman and the audience will need microphones.