Restaurant recommendation: Nicolas Flamel on Rue Montmorency off Rue Beaubourg. Wonderful food in what is reputed to be the oldest house in Paris. You need reservations. Reasonably priced. I would skip two days in the Loire. You are cheating yourself on Paris. Don't do two museums in one day. You can't do the Orsay, Orangerie, and Louvre in one day, and the tickets are expensive. When you do go to the Orsay, you can buy tickets from the magazine stand just down the steps on the right in the front on the museum and not wait in line. Go to the Louvre on a second day.
Read up on the art there before you go to the Louvre and you will appreciate it more. Be prepared for Disneyland-like atmosphere in the room where the Mona Lisa is. However, the long gallery just the left of that one has four Leonardos that you can spend all the time you want looking at. Also Raphaels and many other famous Renaissance painters. The stone with the Code of Hammurabi is in the ancient art section of the Louvre. And don't forget to visit the galleries with art from the Dutch Golden Age, with Vermeers and Rembrandts and lots more. And whatever the special exhibit going on at the Louvre then will be worth visiting. Buy your tickets online before you leave. Or find an FNAC store, there's one in the Les Halles area, where you can buy tickets for all museums and lots of other things. After you come out of the Louvre, stroll down Tuilleries Garden to the Place de la Concorde. And then keep going and walk down Champs Elysees toward the Arc de Triomphe.
The Orangerie is pretty cool. It takes at least 2 to 3 hours to fully appreciate. Another one worth going to is the Petit Palais, and it's free. Also visit Invalides across Pont Alexander III where Napoleon is entombed under a huge dome.
Walk around the Marais and take pictures. Visit the gallieries under the arches around Place des Vosges. Sit down and relax in Place des Vosges, thought of as the most beautiful square in Paris. Visit Rue des Rosiers, the old Jewish section of the Marais.
Walk down Rue St-Louis on Ile St. Louis. Visit the galleries and other shops there.
Get up early every day and take pictures, not with your phone but with a good camera with a good zoom lens. No one is around and you will have Paris to yourself. At 7 AM, few people are around Notre Dame. It opens around 8 AM and you can walk in, take pictures, and there's not a dozen people there. Walk down next to the Seine in the morning and take pictures. (Here is a link with pictures I took mostly in the early morning https://plus.google.com/collection/AJZxoB). Spend time on the left bank visiting art galleries. I would skip the Moulin Rouge. It's expensive and touristy. Go to an organ concert at 5 PM on Sunday at St. Eustache Church near Les Halles. It's the biggest organ in Paris.
Go to the Jardin Luxembourg and spend some time there. Go St. Chappelle on the Ile de la Cite and see some the greatest stained glass windows in the world. Walk down Boulevard St. Germain not far from the Orsay.
Learn to use the Metro, and buy ten tickets at a time in the machines in the station. It's not hard to master the Metro and you can get almost anywhere in about 20 minutes. If you have to change from one train to another, be prepared to walk a bit underground.
I know that I am suggesting a lot, but Paris has so much to offer that limiting your time and trying to see too much, like Versailles and the Loire takes away from many places in Paris that are special. I am writing this from the perspective of having spent a month in Paris for each of the past three years. My wife and I really love that city. Good luck. Have fun.