First, Viator is a third-party broker. If you want a tour, go directly to a tour company. Viator may cancel your reserved tour a few days before, if they can't find an available company. You also save money going directly to the tour company.
However, for Lucerne , there is no need for a tour. You can check the boat schedules and decide how long you want to go out and cruise. Even in winter, the countryside is beautiful. Just ride out to a stop, and catch the next boat back.
We were in Lucerne for the Xmas markets a few years ago, and decided to go up to Mt. Rigi. We took the boat to the Vitnau stop, (1 hour), and the cogwheel train was coordinated to take us up to the summit. If you have great weather, it's a fantastic trip. For us, it was cloudy at street level, but the train took us above the clouds, to bright blue skies and fresh powdery snow. We were above the tree line and above the clouds. I can't describe how thrilling the experience was! (You should be able to find a live camera feed online, to see how clear the summit is, when deciding whether to go.)
This was a half-day trip for us.
Enjoy this beautiful country. Safe travels!
Jungfraujoch is a major expedition if you're staying in the Berner Oberland. It would make for a very long day for you, and a gamble with the mountain weather.
