It all depends if you are going to rent a car or use public transport.
The trip to Montreux and the Chillon castle may be nice but in February, well I am not so sure. This area is really nice in the spring.

A trip to the mountains would be nice but by car, otherwise too time consuming. I'd recommend Avoriaz in France, only one and a half hour away by car. On the return trip a stop at Evian for a typical Alpine dinner.

If you go by public transport, why not take the train to Zürich, beautiful scenery on the three hour trip with maybe a stop at Bern for lunch?
Let me know, I'll give you more info.