Hello,
ILuvParis. I know that you are familiar enough with Paris to try to dissuade your boss from staying at this property. Regardless of the good quality of the hotel, the location is really a problem unless you are in transit or at a seminar.
Everyone posting to this thread is on target with their advice (including that faux-Frenchman, Canista
).
monahos, as usual, offers excellent advice and his information on transportation between Paris and the Hilton, particularly his view on safety, is correct. There have been many security problems on this line of the RER train.
Have you tried contacting by fax the concierge service of the hotel to find out what sort of excursions they can organize? I think that might be your best bet.