Hello Suresh, and welcome to the forum! As far as I know, short stays at high altitudes shouldn't be a problem with your 10 month old baby. Long stays, such as an overnight stay, should be avoided, but visits of a few hours mostly don't cause problems. High altitude sickness can happen to anyone though and it can be recommended to take your time when travelling to high altitudes and to be aware of early symptoms with your baby. Good information can be found on the Jungfrau railways website
and on this website
During you stay in Interlaken your could visit Jungfraujoch and Schilthorn (which are considered to be true highlights), take the cog railway up to Schynige Platte, make a cable car ride up to Männlichen or First, make a boat trip over lake Thun or lake Brienz - and so on. There are many activities which can be done from Interlaken. Please take a look at this day trip overview
and see what appeals to you. From Lucerne, you could get up to Titlis
(from Engelberg), Rigi
. The cog railway up to Rigi is even for free with a Swiss Pass. A boat trip over lake Lucerne
is a wonderful day trip as well. If weather is bad, stroll along the streets of Lucerne or visit the Verkehrshaus (a traffic museum).
You can plan your trips using the timetable
. Timetables for mountain railways and cable cars are often listed at the web sites of the transportation companies. Many of them are listed in this overview
As for rail passes: exact calculations should be made to find out which pass is most economical in your case. This would require you to find out what trips you want to make first. Instructions on this can be found in the rail FAQ
. If you plan to travel quite intensively on (almost) each day of your stay, a Swiss Pass
would be a good option. It offers ease of use, as you can simply get on and off board in trains, buses and boats, without having to purchase tickets for each journey. If, on the other hand, you'll mostly make rather short trips from Lucrerne and Interlaken, a Swiss Half Fare Card
may well turn out to be the cheapest solution.
I hope this gets you started!