Hi Paola, and welcome to MySwissAlps!
>> We are family of 3 adults (21, 46 and 73) planning visit Swiss. We are very interested in the Golden Pass but not quite sure how it works.
The Golden Pass route runs from Luzern to Interlaken Ost past some beautiful lakes and over the Brünig Pass, and then on to Montreux via Zweisimmen. There are several changes of train along the way. You can travel the whole route, or just parts of it. The sector between Zweisimmen and Montreux has panoramic coaches. No reservations are needed, but the trains can get busy, so reservations are probably a good idea, at least between Zweisimmen and Montreux.
More information here:
>> We plan to arrive to Lucerne on June 18 and would like to visit Montreux. Have to return to Paris on a train Montreux-Paris on June 22.
1-I would like to know which is the best route to visit?
I'm not quite sure what you mean by your first question - could you provide a little more information? :)
2-I would like to know which train pass is better to buy?
If you are in Switzerland for 4 days and will be out and about using public transport every day (trains, buses, boats and cable cars), a 4-day Swiss Travel Pass would probably suit you.
3-Do you have any ideas for planning the visit from June 18 to June 21 (4 days): where to go, where to stay?
If you are traveling Montreux-Paris on June 22, it is probably a good idea to spend the night of 21 June in Montreux. The rest of the time you could stay in Luzern, where there is plenty to do and see.
Ideas of what to see while staying in Luzern are here:
For accommodation, I would recommend somewhere close to the railway station in both Luzern and Montreux. Accommodation information can be found here: