Hi Margie, and welcome to MySwissAlps!
>> We are traveling through Switzerland and Italy the first 2 weeks in June and trying to find beautiful and cost effective travel options for each leg: Lucerne to Interlaken (Golden Pass viewing preferred)
The standard route between Luzern/Lucerne and Interlaken Ost is the Luzern-Interlaken Express, which (as its name implies) travels along the part of the Golden Pass route between Luzern and Interlaken Ost.
>> Interlaken to Lauterbrunnen
There is only one train route between Interlaken and Lauterbrunnen, so you can't go wrong with this!
>> local gondolas, funicular, etc.
Please see my post of Apr 29, 2018 - 11:52 PM on the following page for a list of the key mountain transport in the Jungfrau Region:
>> Does it make sense to purchase a combined regional 2-country pass or to buy each each segment separately
A two-country Eurail Pass offers limited benefits in Switzerland compared with a Swiss Travel Pass. I have not travelled extensively in Italy, but I have read that a Eurail Pass is often not cost-effective there because fares are relatively inexpensive. In addition, I understand that many smaller towns and villages that are popular with tourists can only be reached (or are most conveniently reached) by bus, which is not covered by a Eurail Pass.
Once you have decided on a detailed itinerary, including all trips you intend to take on trains, buses, boats and cable cars, the information on this page might help you decide:
www.myswissalps.com/tr ain/ticketspasses/prac tical/chooserailpass
>> and should we buy seats in advance with reservations?
Reservations are the exception rather than the rule within Switzerland. The only trains with compulsory reservations are the Glacier Express, Bernina Express and Gotthard Panorama Express.
Travelling to Italy from Switzerland is a different matter, and reservations are often required. The Swiss Timetable will tell you whether or not reservations are mandatory (or possible) for any given service.
(Use the one on the right with the red SBB logo.)
>> Is the Swiss Half Pass a good option for all of the travel as we also will use local transport of ferries, funiculars, etc. We are a family of 4 with two teens (15 & 17). Many thanks!
I think you mean the Swiss Half Fare Card. It is not a pass, but buying it (one per passenger aged 16+) entitles you to buy tickets at half price. If you get a Swiss Half Fare Card (or a Swiss Travel Pass) you can also order a free Swiss Family Card, which will provide free travel for your 15-year old.
There is only one way to know for sure: plan your itinerary in detail, including all trips by train, bus, boat and cable car. Then look up the full-fare cost of all these planned trips and compare the total cost of separate tickets with the cost of doing the same trips with the Swiss Travel Pass, Swiss Half Fare Card, Eurail Pass etc.
You can find fares in the Swiss Timetable (link above).
It is important to be aware that the fare shown for any trip in the Swiss Timetable defaults to half fare, as most Swiss residents will have a Half-Fare travelcard which entitles them to this discount. Your calculations need to be based on full fares, which are double the default fare that comes up.
There is information and a spreadsheet to help you, which I linked to above.