Hi Naheen -
Welcome to My Swiss Alps.
Your plans are not too ambitious if you can tolerate a fair amount of rail travel.
Please note that , even though the Jungfraujoch is not far from Interlaken, the actual trip takes a while. The other locations and Interlaken are on the main-line rail network with reasonably speedy trains, but at Interlaken, you switch to slower mountain trains to continue onward into the valley of the River Lütschine and then to either Lauterbrunnen or Grindelwald and thence up to Jungfraujoch.
If you look at this map, you can see where those locations are relative to each other in the country.
There are several usefuI maps, but I like that one because, as you zoom in, when you reach zoom level 32, train lines pop into view, so you can also see how they connect those locations. Lots of mountains, so they may not always be straight line connections, even with a fair number of tunnels.
If you click on Points of Interest then Traffic in the menu, you can make the station stops appear for trains, buses, etc.
All that discussion, because you will use the rails a lot.
I'm pretty sure that Interlaken would be your best central base location. Good access to the Jungfrau, not bad for Zermatt, with a scenic option on the way, and a bit of a trip to Luzern, also by a fairly scenic route. Pilatus is close to Luzern ( that is the German spelling that you will see on all the signs). If you wished to visit Titlis you would have to go almost to Luzern, then take a significant trip on a branch line as you near Luzern. Titlis is a rather long trip. Pilatus is easy.
Bern would be your other good choice. Easy access to Luzern, tolerable access to the Jungfrau, a bit of a stretch for Zermatt
Or, maybe somewhere between Bern and Interlaken, such as Thun. Better for Zermatt, not as good for Luzern.
A forum regular, Maggie Horswell, stays there a lot. She might add her thoughts.
You can figure out your times for travel using the timetable. It is useful to note the instructions on the introduction page here:
The timetable defaults to the fastest route. If you wish to guide it to a more scenic route or make a stop at some place along the way, make use of the "via" option in the advanced timetable...which is the SBB timetable. It will work for Amsterdam, as you look at your departure from Switzerland.
A comment about Interlaken.
We usually recommend staying in one of the Alpine villages, where you are surrounded y the Alps - Wengen, Lauterbrunnen, Mürren, Grindelwald. They are more scenic and you are closer to the Jungfrau and a myriad other attractions.
www.swissholidayco.com /Public/Assets/User/fi les/Map-of-Jungfrauregion1.jpg
I suggested Interlaken because of your travel requirements, not because it has any particular Alpine charm. It has frequent main-line rail connections to the rest of Switzerland and on to France, Germany , etc.
By using the timetable, you can figure out if you wish to exchange longer trips to your other destinations for the nicer environment of one of those villages. Each is discussed here:
August is the busiest part of the tourist season, so look into accommodations soon.
Finally, there has been considerable discussion on this forum about taking infants younger than about 2 years up to altitudes over 2000 meters . Jungfraujoch is well above that. The concern is that some people react poorly to the thin air at those altitudes, and that an infant may not be able to let you know clearly if he or she has a problem. Ask your doctor. Some have noted that the air pressure in modern airplanes is maintained at a fairly low level ....about the equivalent of 2500 meters... for comparison.