I have not been there myself, but have been doing research for an upcoming trip. Honestly, Zurich seems pretty dry, but I could see doing the following with kids (age?):

-Exploring the city a little bit- there are some beautiful cathedrals & other interesting sites
-Taking a lake/river cruise/boat taxi
-Getting out of the city a little bit and taking a hike
-Enjoying a local food, particularly chocolate and cheese