72625 posts
Hi drsujoym and welcome to MySwissAlps!
I believe you are referring to the Swiss Travel Pass and it is available in 3, 4, 8 or 15 consecutive days.
For more details on what they are and where they cover, pricing and where to buy them please check out our page on the Swiss Travel Pass here (change your country of residence on the right to see where you can buy them).
For information on other rail passes, take a look at our page on how to choose a Swiss rail pass. It lists several different passes that are available, as well all relevant details on them.
Even with only staying for 6 days, the 8 day pass may be well worth it for as there are many extra included (free local transport in most cities, some free museum entrances and so forth. Details can be found on my link above).
Also, the Swiss Family Card would be perfect for your children – when parents have a Swiss rail pass the children (between 6 and 15) travel for free.
I hope this helps, let me know if you have other questions!
Lucas