train or drive from Paris to Orleans

Have you had experience driving in and around Paris before? I think this is the main criteria for making your decision, especially given the fatigue that you can experience after a long flight.

If you feel comfortable driving in and around Paris, I'd just pick your car up from the airport, otherwise your decision is made - take the train (I think it's the RER B to Saint Michel then the RER C to Austerlitz to get a train directly to Orléans)! In the latter case, it will take you longer to get to your final destination, but the stress levels will certainly be lower!

You don't say, but it sounds as though you may be assuming that you must return the car to the same place you got it. You don't have to! So don't make your decision on that basis.

Thank you for the responses - both are helpful. I probably should have clarified my question a little. We'll be spending 4 days in Paris (definitely without a car!), and will then go down to the Loire Valley for a week. We were originally going to take the train to Orleans and then rent the car there. We will be outside of Orleans until the day we leave - a Saturday (flight out at 14:00). Not sure if it would be easier to return a car in Orleans and then take the train up to the airport, or just drive up to the airport. We have a 5 year old and a 22 month old. Trying to keep stress levels down!

First confirm if the car rental office in Orleans is open on Saturday. If you are committed to staying the last night of your trip near Orleans, then taking the train/RER to the airport may be less stressful than having to drive in all the traffic around Paris to get there.
My personal choice would be to drive to the airport, but spend the last night on the north side of Paris within 30" of CDG. To do this, you could work your way up there on Friday, maybe stopping at Chartres to visit the cathedral and Giverny to see Monet's gardens, and then stay the night near Chantilly.

With small children, car seats, and luggage the train might not be the easist. You can arrange to pick up your car at a location near the autoroute with careful planning. The French highway system is wonderful! The car returns in Paris are dreadful. I suggest picking up the car near the train station in Orleans and returning it to the airport you will depart from and spending your last night near there. The luxury of a car outweighs the hassle every time. I always use AutoEurope.

I, too, like AutoEurope. AE has a pick up point near the Porte d'Orleans metro station which is at the end of line 4 and is close to the Peripherique ring road. You could easily head south from there on major roads.