I was thinking about using the Sennheiser as a boom mic and having the back-up recorder as just that, another source in the room, and amalgamating the two tracks (if this is a bad suggestion I would appreciate your opinion). There is no problem with recording that I’m aware of, they have just asked to have it recorded clearly. I know nothing of room dimensions, but as I understand it a roundtable discussion means that they will be sat at a single table. I was not going to run it through a mixing desk, but I could as I have access to one.
I have found that people are not always aware of what options are available to them and, even if they are, they do not have recording equipment of sufficient quality to get adequate results. I will ask for more information, but that’s what I have at the minute.