Have fun Gina! :)

I haven't read all the posts in depth, so forgive if repeating. The cheese farms are wonderful and fun. WE went to one south of HOnfleur--sort of on the way to Bayeux. It is also fun to see the many cows in the fields--that go with the cheese.
Have you considered reversing your directions and going to Normandy first. I say that because CDG is on the more northern side of Paris and it is easy access to head north.
You could go to Giverny easily from CDG.
Rouen would then be close for your first night.
We loved Bayeux for seeing the beaches. We also had a stop in Honfleur but we were not going on to the Loire.
My comment about your itinerary in particular is that I don't think you could expect to see Giverny and Versailles in the same day returning to Paris from Normandy.
I would also say we really enjoyed driving the "lesser" roads--not the big autoroutes. Maybe called the N roads?
Get the Michelin Green Guide to Normandy and do your own day tour of the beaches from Bayeux==Omaha, Arromanches, Pont du Hoc and the American Cemetery. You will have a good idea of what that landing was, and be amazed. Eat lunch in a town on the water out on the terrace!! Preferably mussels, of course!!

I was thinking that maybe on your last day when you drive back to Paris instead of visiting Honfleur or Giverny you could explore the Pays d'Auge. Of course it depends on how much time you have. Here is the tourist website for Pays d'Auge:

http://www.pays-auge.fr/

You could at least explore its northern portion between Pont-l'Evêque and Lisieux. Take the A13 to exit 29 and head for Beuvron-en-Auge (cute village) and follow the scenic road southeast. You'll see a few châteaux on the map you can pass by. If time permits you can stop at Saint-Hyppolite just south of Lisieux and visit the farm I mentioned previously.

http://www.sainthippolyte.com/

You could then head back north to the autoroute and maybe explore some of the scenic roads near Blangy-le-Château and Cormeilles (both cute villages).

Is it easy to do the D-day beaches on your own and is it possible to do it in half a day? We are thinking of hiring a private guide to tell us the details and show around. Not cheap but if it's worth it, we will do it. I don't know if there are any organized bus tours that are good.

1 FULL day, maybe 2 is needed for the D Day beaches. Maybe 1 with a guide? or if you have a car, its easy to do on your own but you will miss a few details

I've never done a tour but everyone I've heard from on the travel forums who has says it is much more informative with a guide and they usually also do full day tours as opposed to half day tours.

I don't think a half day is anywhere near sufficient to "do the D-day beaches." I've been to Normandy many times and each time spent 2-3 days seeing the beaches and cemeteries. Of course you could be selective and just opt to see maybe one beach and one cemetery and squeeze it into a half day, but given the distance from Paris where most people would be originating, that doesn't make a lot of sense. I've never used a guide, just Michelin and other books. I think the Mémorial Museum in Caen (which for me is an absolute must-see - and it alone can absorb half a day) offers tours.

You cannot really "do" the beaches in a 1/2 day. You can visit Omaha Beach and the American cemetery and skip nearly everything nearby in a 1/2 day, but the nature of the area is that there are battle sites and monuments scattered throughout each of the beaches and you won't go to one central place and view X and get a feel for what happened. I'm surprised you're choosing 5 nights in Normandy over the Loire, but because you are, you should see as much as you can at the beaches.

Thz Bayeux tourist office website (I gave you the link) has a list of guides. I'm sure there are many others but that should give you a start.

Wow what a wealth of great information!
I am bookmarking for our trip in October.

We spent parts of several days seeing the beaches. I am SURE we did not get as in depth as a tour guide would be, but for me, I am also pretty sure I saw and read enough to have a good feel for that enormous landing, and admiration for the heroism and planning.
We used the Michelin Green Guide to Normandy, and then bought the quite good guide books at the places we stopped. There are a LOT LOT of little museums and things along the road that are in my opinion, not needed for a tour.
I would not miss Arromanches nor Ponte du Hoc for sheer amazement. We did go up to St. Mere Eglise, and saw the Pegasus Bridge on the way to Bayeux. Very interesting also, but if it is the Bayeux area, the major US landings can be done.
It really is possible to do it yourself--connect the dots of the sites.
And do not miss the Bayeux tapestry.
We ate the best meal of our French trip that year in Bayeux--Le Petite Bistro (gender agreement!!). Make a reservation. The Cathedral is also very interesting, we thought.

Le Petit Bistro is gender agreement. But do agree it's a wonderful place!