Days 5 to 12 of your trip are a lot like part of our trip to France and Italy last May/June.

We arrived in Paris and had a week there including a day at Eurodisney (Take the train, it is easy and quick and drops you at the door.) We also went to Monet's garden by train from Paris. The train was pretty quick, but you then need to get to the gardens by bus or taxi. We got a bus there, but there was not a suitable bus back and we had a deal of trouble getting a taxi. If you can drive, I would suggest doing that. (We actually drove right past it on our way to Mont St Michel) After Paris, we picked up a car at CDG airport and drove to Mont St Michel. This did not involve driving in Paris at all. We had 2 nights at MSM staying at a hotel http://makeashorterlink.com/?B5F915813 a few miles away from the island. The hotel had a nice restuarant and our room had a view of MSM in the distance. Mont St Michel was one of the highlights of our trip. Try to see it at different times of the day so that you can see the tides. Also, try to get a guided tour of the church at the top as they explain a lot about the history of the place.
>From there we spent 2 nights at a small hotel http://www.claircottage.com/indexan.html in the Loire and went to Chenonceau and Chambord both were really impressive. If you have time, there is always more to see and do in Paris. In addition to all of the places that you have mentioned, I really enjoyed a morning at La Defence and the Cathderal at Mont Marte overlooking the city. Have a great time. If you want further info, post another message. Also, there are websites for most of the attractions that I have referred to. I can give you the details or you can find them by searching (eg using Google). I am sure that you will have a great time.

Peter Quiggin Canberra, Australia's Capital City