I will be in Basel with my family. Any suggestions on how to rent a car? We will use it to drive to

I will be in Basel with my family. Any suggestions cheap tickets to disneyland 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, cheap tickets to disneyland 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 cheap tickets to disneyland 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.