Swiss rail pass worth it and do you need reservations?

1) If you can get a Swiss Rail Pass for the same price as an individual ticket then by all means do that.
2) Best Plan is up to you
3) Depending on what Swiss Rail Pass you have, the discounts will be different, but they should all include some sort of discount for the trip to Murren.
4) You don't buy a ticket for a specific train, you just buy a ticket from point A to point B and hop on the train
5) You only need reservations on certain specific specialty trains like the Glacier Express. Otherwise reservations not required
6) Rail Station is in Geneva Airport as well as Zurich Airport.

Caitlin, Swiss railways doesn't do reservations. That is a foreign concept (literally), except for about 3 tourist trains (like the Glacier Express) and if you are a group of over 10. The trains are usually about 1/2 to 2/3 full.
The tickets are all a fixed price, there is no discount for advance purchase and a ticket is valid on any train on the date on the ticket. Buy on the day and get on any train heading in the right direction.
Your trip will be to/from Mürren, via Interlaken. A ticket from "Genève-Aéroport" to "Mürren BLM" costs CHF 91.60 (2nd class, full price).

You have three options:
1) Full price tickets
2) Buy a half price card (Halbtax-Abo), and pay 50%, i.e. CHF 45.80 to Geneva Airport to Mürren.
3) Buy a Swiss pass, for a number of days.

In order to work out which is cheaper, you need to list all your intended journeys and add up the prices for the three options.

If you want to see where a Swiss Pass and a Halbtax-Abo are valid, see the map here: https://www.swisspasses.com/railpass/overviewmap_en.pdf
All times and prices can be looked up on the Swiss Federal Railways website: www.sbb.ch

Fourth option---a Transfer Ticket which will get them from Geneva airport to the Interlaken area destination and from there to the Zurich Airport, but won't cover anything else.

The Swiss Travel Pass fully covers nearly all train, buses, boats, city trams, and museums. The higher mountain lifts are usually discounted 50%, but the route from Wengen or Grindelwald to Jungfraujoch is only 25% off. Both coverage and discounts work on your counted rail pass travel days. If one of the consecutive-day versions fits the duration of your stay, then there's no distinction between days. If you choose a flexi version of the pass, then you don't get any discounts in between your travel days, unless you pay about $63 more to include the Half Fare Card feature at the time of purchase. The same is also an option when buying the Swiss Transfer Ticket. See https://www.ricksteves.com/travel-tips/transportation/trains/switzerland-rail-passes.

Thank you all. Rail Europe was making it seems like we would be taking a big risk by not reserving seats ahead of time. I think I will figure out the prices and decide between a Swiss rail pass and just buying tickets when we arrive. There is an option of traveling from Geneva airport to Bern, then taking an ICE train from Bern to Interlaken, and the Rail Europe site says: "This train requires travelers with a rail pass to purchase a reservation but we are unable to find reservations that are compatible with your rail pass for this train." Is a reservation really needed for this train, and if so, how would we go about making the reservation if we purchase a rail pass? We would only have an 8 minute connection in Bern. About how much would it cost to make the reservation? Thank you!

By national mandate, there is a train in each direction at every town in Switzerland every hour (normal hours like 6 am to 10 pm). Big cities/tourist sites often more. Fast connections are the norm as the nice people at SBB figure you want to get on your way ASAP and not hang around train stations cooling your heels. If they show an 8 minute connection, they figure you can make it comfortably. So if you miss a connection due to your own lollygagging, there will be another train in one hour at the worst.
Stop looking at RailEurope and start looking at www.sbb.ch/en. They run the trains.

Caitlin, You were using Rail Europe? That was your big mistake. It is a reseller which marks up prices, and many on this site advice against it. Always go to the company running the trains, In this case Swiss Railways: http://www.sbb.ch/en/

They are lying to you about reservations. ICE (German high speed trains) are reserved when they are in Germany, but once they cross onto Swiss tracks, Swiss rules apply, it is the same as any other Swiss train and any ticket is valid. The reason it can't find any reservations is because they don't exist.
You don't have to worry about which train to catch until you get to Geneva airport station (under the terminal), then just catch the next train. There is a train to Mürren (changing at Bern and Interlaken) every half hour! Look it up for yourself on http://www.sbb.ch/en/

An 8 minute connection is normal and enough time (as long as you can carry your cases). The trains are designed to work that way. They may even be on opposite sides of the same platform.

Thank you all - you've been enormously helpful. I am excited for this trip!