Advice on last minute Switzerland visit

With only 8 nights in Switzerland, why do you feel the need to go to 4 different places? 3 is plenty. It will take nearly 4 hours to get from Geneva airport to Zermatt, then 3 hours to get from Zermatt to Wengen.
2 nts Zermatt, late afternoon departure gives you 1 1/2 days there, considering arrival day is jet lag recovery.
4 nts Wengen, mid morning departure will give you 3 full days in the B-O.
2 nts Luzern, that will give you 1 1/2 days there.

I agree it might be better to stick to 3 places and not bounce around so much. Why don't you just add a couple of days each in Wengen and Lucerne? This would also give you flexibility with weather if you are planning to do skydiving/parasailing and hiking. Lucerne has a huge, beautiful lake and you can rent boats or paddle boards, swim, take a lake cruise etc. and get the full "sunshine/lake feel" without more long train rides. Plus there are tons of activities and worthwhile daytrips nearby - you can't have tried them all before :) If you don't want to stay right in town, you could stay a bit outside or at one of the smaller lakeside towns nearby and enjoy the more relaxed pace while still having good access to Lucerne and nearby mountains.

If you are set on a different lake destination, you could also look at staying on Lake Brienz or Lake Thun, not far from either Wengen or Luzern. Montreux could be an option (2.5 hrs from Zermatt, 3 hrs to Wengen) as it has good transport links, although it is still a bit out of the way.

Thun is quite lovely. It has a castle, cobblestone streets, small town charm, and the beautiful Aare river running through it. It has a wooden bridge much like the one in Lucerne, and on the opposite side of the bridge where the water flows fast, people actually like to surf. It is also on the very beautiful Lake Thun. It would be a great place to spend a night on your way to Wengen.

Thank you so much for your replies. You are all right as it is moving too much.

I’m booking 4 nights in Wengen and then will find some new hikes and places we have not done around Wengen area.

We only spent a day and a night in Lucerne by the bridge in the city last time. I think your idea of staying 2 nights by the lake is great. Is there any little lakeside town that is accessible by train that you would recommend? That will give my husband the lakeside / water fix he needs:)

I have read about Thun as well and maybe a boat ride and the train back is a possibility.

Thank you all again for your feedback, setting me straight to not do 4 places:) and giving me the best ideas to pull this trip together.

Not that I have ever been there, but the Seehotel Pilatus in Hergiswil looks like it might fit the bill. Lakeside and a short train ride from Luzern.
https://pilatushotel.ch/hotel-news/welcome.html

The classic lakeside resort towns are Weggis and Vitznau. If you plan to visit Rigi, these are perfectly located as they both have direct access to the mountains. They are also stops on the lake cruises. However, Lucerne is about 45-50 mins away by public transport (the lake is a weird shape and makes train access complicated). Better to go into Lucerne via a scenic ride on the boats. However, this is only practical if you just visit Lucerne as a day trip. It may not work at the end of your trip, as it's also less practical for getting to the airport.

If you want to be a short (<20 min) train/bus ride from Lucerne, there are a few options. Hotel Balm in Meggen (nice 'suburb' of Lucerne) is a 15-min bus ride from Lucerne train station (stop in front of the hotel, bus runs frequently from early to late) and has great views, an outdoor pool, and a highly regarded restaurant. You can walk down to the lake itself in about 10 mins and there is a cool little castle you can walk to as well (Schloss Meggenhorn).
The towns of Kastanienbaum, Hergiswil, Horw, Stansstad, or Küssnacht am Rigi might also work, but I don't have any specific hotel recommendations.

If your budget allows, you could also have a look at the lakeside hotels in Lucerne. These would offer convenience to the city with the more relaxed setting you're looking for. Not sure what prices look like this last minute though..