For travelling to/from Paris, you may want to take into account that there is a long-running strike at SNCF, the French railway company which impacts the traffic 2 days over 5 until end of June. Look at the current calendar of the strike for details (dates with a red circle are the days of strike). According to the current schedule, travelling by train the day before the workshop or the week-end after may be difficult.
The strike doesn't affect most of the common transportation system in Paris, with the exception of the RER between Roissy and Paris on the days of strike (you may have to take the bus and expect a longer journey). RER between Paris and Orsay is not (or very marginally) affected.