People in Switzerland tend to plan their non-work appointments with almost the same discipline and forethought as they would their business lives. That's why I wrote that you should contact them in advance, and by advance, I mean as soon as you know you'll be travelling here - even if that is two or three months ahead. If they're busy and you are, they might even agree to a coffee before work or a drink afterwards, just to see each other for half-an-hour. The longer warning they have, the more likely they are to be able to make time to see you. I hope they do!