Being a 'Morbihan' Veteran of 3 rallies so far, I can say it is great fun! You find that the first rally day is the 'Ile D'arz' meet, generally this held on a Tuesday, boats gather at a stone jetty on the east of the island,be prepared to dice with close on a 1000 other boats , get there early if you can ,the queues for the welcoming party stretch for some while, be certain to take some utensils with you .(always handy in France)
This will set the pattern for the rest of the week, at every port you visit, the townsfolk lay on some form of refreshments , sometimes you have to pay for it,but wine is literally free flowing!!
the event is well served by safety boats, is as well, as there are some fearsome tidal rips around some of the islands, if you don't make the tidal gate ,you most likely not get through to the next meet point.
Launch & recovery can be a nightmare, especially if you got your designated flotilla launch site, last time I went ,we launched at another flotillas home port,Our boat was in the sail & oar fleet ,we launched at the small cruiser fleet.
The Semaine du golfe is a tremendous experience, the like of which you never see in our home waters, that said I am unlikely to go this year it has become a bit of an uncontrollable monster, every Frenchman with the most humble of boats tries to get in on the festival.