Hi Mathilda, and welcome to MySwissAlps!
>> our first question-what is best way to travel from gimmelwald to Zurich airport in September? ... how many times will be need to make transfers?
- Cable car from Gimmelwald to Stechelberg
- Bus from Stechelberg to Lauterbrunnen
- Train from Lauterbrunnen to Interlaken Ost
- Train from Interlaken Ost to Zürich Airport, with changes at either Bern or Luzern (depending on route chosen)
I would avoid any connections requiring an additional change at Zürich Hauptbahnhof (main station), as that will slow you down a bit.
>> we would like to catch a three o'clock flight to Ljubljana. do we have time to take the scenic route through Lucerne?
Yes, if you leave early enough. The trip from Gimmelwald to Zürich Flughafen (airport) via Luzern would take about 4.25 hours, plus any time you wanted to spend in Luzern. I don't know how early you have to be at the airport for a flight to another Schengen country, but it's probably less than 2 hours. You would need to check with your airline.
You can plan this trip (and any others you intend to make within Switzerland) using the Swiss Timetable:
>> Is there one train pass best suited for our travel as we will also be arriving at Zurich airport and travelling to mereigen(Reuti)spending a day or two- taking cable cars to high peaks and then going to gimmelwald for two days. Please recommend the best train pass and train routes.
There is only one way to know for sure: add up the full-fare cost of all trips you intend to do by train, bus, cable car and boat and compare the total cost with the cost of doing the same trips with a Swiss Travel Pass or Swiss Half Fare Card.
There is information and a spreadsheet here to help you:
www.myswissalps.com/tr ain/ticketspasses/prac tical/chooserailpass
If you can't be bothered doing the sums, you could simply get a Swiss Travel Pass for 4 days and point-to-point tickets for the 1st or last day, whichever is cheapest. (That is, if you decide on the extra day).
You can download a map from the link below, showing what is covered by the Swiss Travel Pass in 2018.
As explained in the legend on the map, red lines are trains, yellow lines are buses, black lines are cable cars, white lines are boats. Solid lines are free, dotted lines are discounted. Discounts are mostly 50%, but only 25% for transport where you see the number "1" inside circle near the dotted line. There are a few grey lines on the map as well, which indicate transport that is not covered by the Swiss Travel Pass. Dashed red lines on the map indicate railway tunnels, and are on routes that are free with the Swiss Travel Pass.