There are 4 of us wanting to go to Aix en Provence. Would renting a car (have international drivers license) since two of us are elderly?
Are you arriving at one of Marseilles Airports? Identify which one. Some have direct trains or buses to Aix en Provence. I believe that Marseilles Provence Airport is where you can buy a train ticket at a kiosk for abt 6.50 Euros. Aix is less than a half hour away by train. So you might want to wait to rent a car depending on your future plans after arriving in Aix. P.S. Be sure your Luggage is easily transferred!
It's about a 40-minute downtown to downtown drive but you first must go through the rigmarole of finding the rental office and hiring the car. At the other end, parking. The regional TER train takes about the same time but the Marseille train station is just off the downtown and the Aix-en-Provence station is inside that town too (for the regional trains, not the TGV station.) That sounds easier to me. The region has a multitude of bus services that may serve A-i-P since it is almost a suburb.
From Marseille Provence airport there are frequent, cheap bus shuttles to A-i-P. A taxi, divided among four, will be cheaper than a day's car rental, I think. There's plenty of useful transit information on the airport website, https://www.marseille-airport.com/
Do not rent a car just for the drive between either Marseille airport or Marseille Downtown and Aix. In the first case, buses and taxis work fine, and in the second case, there are very frequent buses and trains too. Traffic between the two cities is very bad, and driving in Aix is a nightmare due to one-way roads.
driving in Aix is a nightmare due to one-way roads.
And driving in Marseilles is not a piece of cake either. That is, if we're talking central Marseille as opposed to Marseille Airport.
From the Marseille airport, going to Aix-en-Provence is the same distance as going into Marseille. It would make no sense to go into Marseille just to rent a car to drive to Aix. Either rent a car at MRS, or take the bus into Aix-en-Provence and rent a car there.
The credit card used for the rental must be that of the principal driver. This can sometimes cause problems if a non-driver wants to pay for the rental. This may or may not apply in your case.