Car rental instead of train from Paris?

Remember that the cost of driving is not just the cost of renting a car, it is also road tolls, fuel and parking. And those costs can easily add up to hundreds of euros.

It is also travel time, Paris to Bordeaux is 2 hours by train, compared to 6-7 hours of driving.

Driving from Paris to the Dordogne is not "nuts". It takes 6-6.5 hours (vs 2 hours from Bordeaux) depending on where you are going, and tolls are perhaps 25€ on that route, no more.
Rent a car at Gare de Lyon: it is close to the Marais, and getting out of Paris is pretty easy from there.
Or if the Paris bit worries you, you can travel to Orly airport and rent from there. You'll save the first 20-30 minutes of the drive out of the Paris metro area.

Cost aside, I wonder if it would be easier with all our bags and chair to rent from Gare de Lyon?

If you need an automatic car you are better off renting at airports and big train stations.

There are some wonderful spots along the way between Paris and the Dordogne -- if you could make the trip in two days you could make a couple of nice stops along the way.

We won't need automatic.

Yes, now I wish I had put more days headed south and then headed north again. I basically threw this trip together in a week during displacement from our home for 4 months with water damage, so I had no time to work on it, ha ha! But, at least we are going. I had found cheap tickets we could use our miles on so I jumped!! We have rentals homes week to week, so we will have to stick with our time frame.

Cost aside, I wonder if it would be easier with all our bags and chair to rent from Gare de Lyon?

You will need a taxi from your Marais accommodation anyway, so whether you go to Gare de Lyon or to Orly to rent the car does not change much to the logistics.

But yes, I agree that in either case it will be easier and smoother than to first take the train to Bordeaux with all your stuff.

A word of warning: make sure you rent a large-enough car! Cars here are smaller than in the USA and trunk space is tight in many models.

Oh and regarding Avignon to Paris: the train is almost 3x faster than driving for that one, so do stick with the train.

To help you in your budgeting, go to Via Michelin and input your rough origin and destination points - it will calculate for you the cost you will spend in fuel and tolls (you can either stick with the default size car they pre-populate, or you can modify the type of vehicle).

Thank you everyone! I just booked trains both directions and went with the cheaper OUIGO train. We may just take a taxi from our apartment to Montparnasse or it looks like the bus is a good option as well. So glad to have that dialed in!

Thank you for all the help and thank you Andrea for the FaceTime help!!

Bus 96 is direct from the Marais to Montparnasse but bus reliability is low in Paris, and if you have a lot of luggage it won't be very comfortable. A taxi is about €20.

Susan, I’m always happy to help. For that matter I can come along and help you tote your bags or push P’s chair. I know you won’t mind footing the bill. 😉

We can get Jim to drive us to SFO…

I know you have no alternative, but be aware (my own experience) that a transport chair (with swivel 4" wheels) can be a trial on cobblestones. While you have the car remember that visible objects attract thieves while parked - even indoor, upstairs paid parking. (Rick has wryly joked about paying a Bogus Parking Warden (elderly pensioner in a vest, earning extra money) to watch your car ... .One more car issue, if you drive in medieval city centers, larger cars can break their mirrors off going through archways or around tight parked cars. You want the smallest car that will do the job for you.

It has also been my experience that municipal parking garages in Europe have much smaller stalls and much narrower auto ramps and passages than we are used to in the USA.

Thank you balso! I think a taxi will be much easier and better for us. I had no idea of price, so its very helpful to have an idea and well worth cost.

Andrea, certainly! We do need need a wheelchair pusher! You and Jim are always eager to help us :-)

Tim, thanks for that info. We actually have taken a transport chair to Paris in the past. Monte was exhausted trying to push it all around! But, he says he's up for it, so we will just have to work around it and only do what we can. Thankfully, our daughter can walk, it's just distance that is difficult for her. We even took the metro and he lifted the chair over the turnstile without anyone stopping us, so hopefully we can do that again? As far as the car, we have driven in France in the past as well, and took the chair with us, but now I don't recall what size car we ended up with. I recall it worked ok for our luggage and the chair. I rented a PEUGEOT 2008 OR SIMILAR MANUAL COMPACT CLASS. I'm hoping it will hide all of our stuff, but really it will only need that if/when we stop in route between our accommodations.

On the metro there should be a wide gate that can be used for people in wheelchairs or pushing a stroller. I’ve used those occasionally when I have luggage.

On the metro, some stations have wider turnstiles but most do not. At the main entrance (and at most secondary entrances) there will be a metal gate with a buzzer next to it: that's where you should buzz if you need to go through. You buzz, someone opens the gate, you all validate your passes or tickets at a turnstile next to the gate, and you go through. It can be cumbersome, but it usually works.

Thank you! I’ll make sure we look for that!