German and France trains

Just look up the web sites of the SNCF and the DB and compare fares:

https://www.sncf-connect.com

https://int.bahn.de/en/

Compare prices on both the DB Navigator and SNCF Connect apps. Schedules won’t be available yet for those dates. Prices go up as travel dates approaches, so book as soon as possible. Looking at options in December, prices are about €150.

I will do this trip for 80€.
ICE highspeed from Saarbrücken to Paris-Est, TGV Inoui highspeed from Paris-Montparnasse to Bordeaux.

Both ICE and TGV offer a limited selection of cheap tickets for early bookers.

Your ICE ticket is available 180 days in advance (April is already available for €30/person).

Your TGV ticket is issued 120 days before departure. Wait another month and you can buy it for €50 per person.

Lessons learned? Limit your information to that provided by local people and pay less money.

Be aware that in Paris you will need to transfer from Gare de l'Est to Gare Montparnasse. You can take the No 4 Metro or a taxi.

I'll just add that on at least the Paris-Bordeaux leg if you are traveling solo the 1st class compartments offer a line of single seats down one side of the car. Buying well in advance, 1st is not much more than 2nd class. You would also have the ability to pick your seat when you purchase your ticket. There are a couple of threads going about luggage on trains with some folks having recently had bags being taken. I usually try to get the seat that is right across from the luggage rack so I can keep an eye on my bag. This may not be a concern of yours at all but thought I'd mention it.

Gare Montparnasse has a good selection of food kiosks if you want to get food for that half of the trip.

Thanks for all of your advice. I will make our purchases accordingly. I also appreciate the transfer information.

I would wait till you can book the whole trip in one purchase, and do so on SNCF Connect, as you will be travelling on French trains exclusively. (Saarbrucken is the station where DB hands over its trains to SNCF, so beyond that it is SNCF that operates, even when the train set is a white German ICE set...)

You will have to wait about a month until April opens.

The metro is easy, and line 4 is one of the lines that has been modernised. But you will need to get tickets. Easiest is to get the Navigo App for your phone, and buy a single metro ticket.

Which APP specifically for Navigo?
Overall, this is great information for me. Thanks to all.

With luggage in tow I would not take Metro from Est to Montparnasse.

To avoid that I take bus # 91 which stops right in front of the main entrance gate of Est, the big restaurant is located opposite of the bus stop. That's where Bus # 91 starts, I have ample room for my spinner as I stand in the standing area (middle of the bus) instead of sitting down.

The bus has the added advantage that you can now just pay with your credit card. Finally...
(Which gives hope that this will finallly work on the metro as well...)

But a taxi would also be an option.

For the bus 91 and the Metro I use the Navigo Easy card...very convenient.