The wife and I did one several years ago,$299 each for seven days through Dargal.com. I haven't seen one at that price in years though. It was nice, although we were the youngest on the ship by far.

Someone else mentioned the rent your own boat. We rented ours through LeBoat.com and it was a blast. Very Leisurely, met lots of great people, drank lots of fresh wine (not that old stuff! ). Also look for locaboat.com.

If you don't want to drive yourself, try: Enchante we got a tour, and it looked very nice, and the smell from the kitchen was amazing.