Hello! A group of us (4 women, late 20s) will be in Switzerland for a conference in Bern during Easter week.
We are planning to fly there on April 20th and arrive the 21st which is Easter. Do you know if everything will be closed that Sunday? Any recommendations of what we should do that day? Primary goals are seeing the culture and variety of things unique to Switzerland, also keeping in mind April as a shoulder season. We are thinking boat rides, thermal spa/sauna, beautiful lake and mountain views, great food (cheese and chocolate), castles, museums, cultural sites, walking around.

Here is the itinerary we are thinking of - it just seems so short!! Please advise your must sees!

Easter Sunday, April 21st: Arrive Zurich (travel by train to Interlaken or lucerne for 3 nights)
April 22nd - 23rd: Interlaken/Lucerne with day trip to Zurich and maybe surroundings
April 24th - 26th: Bern (conference - though could potentially stay in interlaken or do shorter day trips in afternoon)
April 26th - 27th: Montreaux
April 28th: Return to Zurich, fly home

You should know that not just Easter Sunday, but also Easter Monday, is a legal holiday in much of Switzerland. So much of the local populace will have the day off work. Not sure if this means that trains, buses, boats will be on the holiday schedule for these two days? But certainly, cafes and excursions will still be "open."
Not knowing that Pentecost Monday was a recognized holiday in many cantons a few years ago, we actually learned of a few cool festivals and fairs on those dates. I expect that Sunday will be the quieter of these two days.

Additional transport sites:
www.zsg.ch (click on English) for boat trips on Lake Zurich. Several trips run from Zurich to Rapperswil, a lovely town 1 hr 50 mins away, on Easter Sunday--train back to Zurich in 20-30 minutes.
www.sbb.ch/en for train schedules and a better idea of trip durations...Zurich airport is just one hour from Luzern. I would definitely overnight in the much more scenic town of Luzern.
Finally, boat schedules for Lake Brienz and Lake Thun are at www.fahrplan.bls.ch . It looks like Spring boat travel begins in early April there as well (reduced schedule).

I believe you can get all the schedules -- train, bus, boat, anything public -- on the sbb website. You probably need to specify advanced search to get to the options for transport other than by train.

BTW, consider giving Bern itself some time -- it's a lovely city!
If you haven't already seen it, you might find some useful information in my trip report:
https://www.fodors.com/community/eur...thanks-983126/

For your train trips it seems a Swiss Travel Pass may be best - 8-consecutive days to cover all your train, bus, city transit and boats - just hop on no need to go to ticket windows - www.swisstravelsystem.com; BETS-European Rail Experts and www.ricksteves.com.

We've visited Switzerland over Easter a few times - our fears of everything being closed were unfounded. We had no issues whatsoever finding restaurants open, although places like grocery stores will probably be closed.

This probably won't apply to you, but Easter is a very busy time in ski areas.