Montparnasse area

If you could give your budget requirements, that would be helpful.
Montparnasse Bienvenue is the large station that will probably be where you will be departing from.
There are normally several stairways in all Metro stations, and you only have to follow the overhead signs if you have to change Metro lines. It will take you all of 3 minutes if you have to do this.
Not all Metro stations have escalators, and they aren't always in service.
It would be best if you do not have heavy luggage that you can't manage to carry up stairs yourselves and into the trains.

We stayed here the last time we were in Paris, as we were departing for Bayonne out of Montparnasse.

Hotel Appollon

I've stayed at Hotel de la Paix Montparnasse on Blvd Raspail. Small hotel, nice staff, not that expensive. I walked to the Montparnasse station from there to catch the train to Lourdes. I don't know if your stair concerns are about luggage or health/physical fitness. Even if you can't do the 15 minute or so walk to the TGV station (from the hotel I mention), it's a short taxi ride.

Re: Aquitaine line TGV - I took 2nd class 4 years ago. They may be using different train equipment now, but I had no issues with 2nd class during that May. I bought a sandwich & drink at the station and later got a coffee and snack in the cafe car. I probably also brought my own snacks or piece of fruit. It's a long day so be prepared with something to read or listen to & snacks.

Hi, our budget is is less than 150 euro per room per night if possible. There will be 4 of us so we will need 2 rooms for possibly 3 nights. As of now, we are looking at either Hotel Mistral or Ibis Paris Gare montparnasse 15eme or Ibis Paris Alesia montparnasse. All 3 has aircon. We will have light carryon and have no mobility issues. Having free breakfast will be an added plus but main issue is safety as we will be out till late( only 2 fulls days in Paris), Very close to take the earliest train to lourdes, and if close to the tower although I think this will be farther from the train station. From lourdes, we will use Toulousse to fly to lisbon ( our homebase for this vacation).Thank you very much for your help.

Thanks Rachel. We will look into hotel de la paix.

Hi Sally,
You don't say when you are going, but I'm a big fan of hotel Lenox Montparnasse on rue Delambre. It has AC, minibars, an honor bar in lounge, and wonderful staff. You should be able to get their cheapest room for under 150 euros.

Sorry, I forgot to include our dates are possibly July 4 check in and check out July 7.