Best thoughts for you, your wife and your family. May you find equanimity and revel in the small things life brings.
The wiki does a good job of presenting the different fixed income options: Short guide to CHF fixed income options
As stated by @Dr.PI, 0% is the current risk free rate in CHF. If the SNB lowers their policy rate some more, 0% checking/savings accounts will be a great deal, providing more returns than banks themselves get on short term cash.
For longer term vehicles, I would look into medium term notes, possibly building a ladder of them if I wanted to preserve some rebalancing possibilities.
Pillar 2 can be used to amortize a mortgage on your primary residency so if that’s the targeted use for it, you should have no problem withdrawing it. There is a 3 years lockup period for buy-ins and you can withdraw only every 5 years so you’d have to plan how you intend to use it ahead of time in order to make it as peace of mind preserving as can be.
You may want to study the insurance part of your second pillar and that of your wife if applicable in order to best understand what they can do for you in your situation and if having more of it, or depleting it, would be a good option (I’d look at the disability and life insurance for both the partner and children (if applicable), as that coverage can also help with hardship).
I’d personally choose between:
- medium term notes ladder
- corporate bond fund (Swiss or hedged to CHF)
- 2nd pillar buy-in