2 day trip to Beaches of Normandy and Mount Saint Michelle?
 

We will be in Paris for about 4 days - and then going on to Spain and Portugal. We would like to go to the Beaches or Normandy and Mount Saint Michelle...
Is it possible to do both in 2 days - leave early one morning for the Beaches then stay overnight go to St Michelle the next day and back to paris for a flight out to portugal?
How should we get between the cities? And where should we stay?
Thanks

I should state that we would like to go to the beaches of normandy and mount saint michelle after our 4 days in paris and before we go on to spain/portugal. and where to visit the beaches? I have seen both caen and bayeaux....

If it's the Normandy landing beaches you want to visit, you could certainly do those and Le Mont St-Michel over 2 days, as they're not that far apart.

However, if it's beach-beaches that interest you, the main areas would be Trouville and Deauville, both resort towns. You could spend a night in either of them, head for Mont St-Michel the following day (leaving your belongings at your hotel if possible) and then return to Paris. That would make for a short but nice trip. You would probably want to take the TGV from Paris to Rouen and pick up a rental car there.

Actually it is just the Normandy landing beaches that we were interested in. We were thinking of extending that part to 3+ days and renting a car and driving out and back. Do you think that will be too much? Or should we just take the TGV out there and then rent a car?

Unless your very nervous about driving the car out of Paris, why not just rent it there and save the price of one or more train tickets? The drive from Paris to Rouen is about as effortless as it gets.

Mont St Michel can easily be done in a day (that's how most people do it), but the Normandy Beaches might be a little more challenging. We spent an entire day there last October and only saw about one-third of the invasion-related sights. If you decide to do this in one day, collect as much information ahead of time as possible and prioritize your visit. There are so many museums, invasion landmarks, etc. that you will have to make some choices. The area around the American cemetery at Colleville-sur-Mere might be a reasonable place to begin. In addition to the cemetery, there is a small (but interesting) museum and a cluster of German bunkers.

Three days is certainly not too much for le Mont St-Michel and the D-Day beaches.
You can easily drive from Paris, but if it makes you nervous, you can also take the train (there's no TGV) to Caen and pick up your car there. I'd plan to spend a half-day at the Mémorial museum in Caen, then head to the beaches. You might want to spend your first night in Arromanches. There's a cute little hotel there right on the beach called the Hôtel-Restaurant de la Marine. The restaurant serves wonderful fresh seafood dishes.
Next day you could continue down the coast to the main beaches and American Cemetary and Pointe du Hoc and Ste-Mère Eglise. You could spend the second night somewhere near there or go part of the way to le Mont St-Michel (Granville or Coutances or St-Lo, for example).
I'd plan to spend about a half-day at le MSM. That will give you time to either drive back to Paris or get back to Caen and take the train.

While we spent 5 days in Bayeux last August and saw more than the D-Day sites and Mont St Michel, here is how I'd do the two areas you're intersted in. Stay in Bayeux if at all possible. Schedule a tour with Col Michael Chilcott (google to find him on the web) - he's a retired British Army Colonel and owns a B/B near Bayeux. We had a full day tour with him that extended to 1.5 days. That covered Omaha beach, british, german and American Cemeteries, Longues Battery, Pointe Du Hoc, Arromanches. We took a separate trip by ourselves to the Mont, Utah Beach and St Mere Eglise. Start early, go to the Mont and go thru St Mere and Utah beach on your way back. If you have any additional time, see the cathedral and tapestry in Bayeux. We drove from CDG right to Bayeux and then back to CDG, dropped the car and spend another week in Paris. Stopped at Giverney on our way back to Paris. Plan 2-3 hours each way.

Just wanted to say thanks so much for all of the feedback and advice! I think we will be fine renting the car in Paris and driving from there.