This happened to me one time with a Savings Fare (then Dauer Spezial) ticket in Germany. I used the login on the Bahn that I had created years before, using my nickname, but my credit card that had to be used for ID had my given name. When the pdf file arrived and I saw the discrepancy, I phoned them right away. The man on the phone said he couldn't do anything about it, but 10 minutes later I got a new pdf file with the name changed.
I later contacted my bank, and they would have reissued my credit card with the nickname.
Have you seen the ticket yet? Does it have their names on it? I don't know what RailEurope does, but most full fare tickets I've seen have not had names on them. Discount tickets have only had the name on the credit card, not other co-travelers. And I don't think your passport will be checked nor do I believe they would compare it to the name on the ticket.