I agree with the two posters above -- think twice before you decide to drive.
Most folks will want to ascend the mountains and visit some of the mountain villages, and you cannot do that by car. If you pay full fare for those trips, it will be hundreds of chf per person. So, most likely you'll get some sort of pass or discount card to reduce the price for those train rides. And once you have that pass or discount card, then getting to/from the airport becomes a more competetive price.
I would suggest you investigate the Half Fare Card, which costs 110 chf and then gives you half off practically everything that moves in the country. Alternately, you can get the Swiss Card, which costs 186 chf per person -- it gives you a round-trip from the border to your destination, and half off transportation for those dates in between.
Anyway, have fun as you plan!