Feb 18, 2015 - 2:29 PM
Those two scenic trains are wonderful! You can take a look at railbookers.com/classic-glacier-and-bernina-express. This is a package combining the Glacier Express and Bernina Express, but the good thing about Railbookers is that they can customize the package for you. So you can stay longer in towns along the way and your point of entry/departure can be different too. Just have a look and if you like the basics you can click the "Send a request" link at the top right of their page. They will get back to you with a proposal.
If this is not what you like you can have a completely customized trip, not based on a package, through Magic Switzerland by filling out a request here.
Finally, if you book this yourself, you indeed need a pass. Which one depends on the details of your trip: how long do you stay in total, which day trips/cable car trips do you plan to make? Once you have listed that you can do the math. All about the Swiss Travel Pass Flex can be found here.
I hope this gets you started!