Thank you so much for the replies.

I was able to book the tickets for the cheaper fares mentioned above on the DB Bahn website. They were much cheaper there than on Rail Europe and we were able to benefit from purchasing in advance. It would not let me print the tickets, but they said they would mail them within the next week (perhaps because I live in the US). I am hoping the tickets arrive and are in good shape as the website was slightly confusing (but much better than OBB, as mentioned).

For anyone else looking to book trains, I found this website which was enormously helpful

http://www.seat61.com/