Bahn Cards

They will send you the Bahn card data that you need as a PDF (as well as a card - although i don't know if they mail the physical card to the States, but you don't need it anyway as long as you have the PDF).

joyflight, which Bahn trial card are you buying? The 25, 50 or 100? If you are buying the 100, it doesn't matter if you cancel since the card is good for unlimited trips.

I believe that if you have the 25 or 50, you would need to use specific restrictrictions in place for tickets which says that you have a 12 hour window to cancel. You can find more info here. But it depends on the ticket. If you buy a ticket that is non-flexible, you're stuck with that day and time. Or you can pay more, and get more flexibility.

With regards to some of your questions, you should definitely download the DB Navigator app. You do that by first setting up an account online and then going to your phone and getting the app. Once you have the app, the tickets will appear on your phone.

If there are 2 people, each person will need their own Bahn card.

If you are buying the 100, it doesn't matter if you cancel since the card is good for unlimited trips.

But please note that the price for a Probe BahnCard 100 is €1295 (2nd class, €2339 1th class), so you probably would have to spend all of your holidays on trains to break even ;). For cancellation rules look up this link: https://www.bahn.com/en/booking-information/exchanges-refunds

Please be aware that DB BahnCards are of no use in the Netherlands and Austria (with the exceptions of international trains run by DB itself). So in the end it might be more economical to buy saver fare tickets.

You can buy 2 tickets with Bahncard discounts under one account. The tickets work fine as long as you can present 2 right types of Bahncards to the ticket inspector on board.