The train is very expensive unless you get some type of pass. But a pass may be worth it. A car rent

I will be in Basel with my family. Any suggestions on how to rent a car? We will use it to drive to Bern and up to get close to Jungfrau. The train seems very expensive for the 4 of us. Our 2 Swiss friends may join us, too. Also, we plan to take day trips into Germany and France. I was planning to rent a car for one day. Looking at train fares, it may be better to rent a car for 3 days. Any ideas would be helpful.
The train is very expensive unless you get some type of pass. But a pass may be worth it. A car rental for less than a week tends to be quite expensive too, but being in Basel, check if French prices are cheaper than Swiss prices; you would pick the car up on the French side of the airport.
I was looking into renting a car in Basel and the least expensive option was taking the train or bus down to Mulhouse, France. It is about 30 km from the BSL airport and there is a rental place very close to the train station in Mulhouse, walkable, at least the Hertz office is. It appears you don't pay the extra fee for picking up a car at a train station. You might have to pay for the sticker to drive in Switzerland but you can try to get a vehicle with a valid sticker.
Taking into account the cost of the bus fare, 15 per person as I remember? I had considered it when picking a car up in Basel but decided that the cost would pretty much even out the 30+ for the airport pick-up.