Purchasing 4 Swiss Travel Passes from SBB

Yes, you can buy them at the Geneva Airport train station and board the next train to your destination. They will cost the exact same in CHF as they do online. make sure to make it it known that you want the transaction in CHF, as they will ask if you want to do the transaction in your home currency. The currency transaction will not be in your favor. Last time I was there, that option (DCC) was presented on the credit card machine screen and you had to press "decline" or "no".

Thanks Sam, so there is no surcharge for buying them in person? Any idea how busy the counter will be on a Sunday morning around 8am? Don't want to spend my day in line...

Probably not too busy. Swiss people will just be buying tickets out of the ticket machines, so only visitors will be at the ticket windows. My experience is that it is a non issue. Just make sure your credit card company knows you will be in Switzerland.

As far as your question about on-line transactions, just use the customer service contact page and ask your questions, They are very good at answering. You might get an answer today. Tomorrow is a holiday, so for sure you'll have an answer by Wednesday morning.
https://www.sbb.ch/en/meta/contacts.html/content/internet/sbb/en/meta/kontakte/ticketshop-onlinetickets-mobiletickets

The Swiss Travel Pass doesn't offer a group discount. All the adult passes will automatically be separate and with individual names on them. Consecutive-day passes are available to print at home, but flexi passes are not.