Hi Chalkpink
Zürich is wonderful.... We moved here 3.5 years ago (before DC) and no way am I moving anywhere else. It's a more old fashioned way of life here in many ways, but kids can be kids, play out, do loads of healthy stuff etc.
Lots of things to do with little ones, summer is all about the badis (swimming places / beaches at the lake) and parks, winter mountains, sledging etc.
google Strandbad Mythenquai, Zürichhorn, Bäckeranlage (park) Park im Gruene, Knies Kinderzoo for a flavour of the types of things.
There are English playgroups (mostly in the city) and quite a few English / American expats who are all pretty friendly, meetups at Starbucks etc.
Private childcare is v expensive but I think it's very good quality of care - my dd is at a bilingual nursery as I work, and it's wonderful. Nursery is called Kinderkrippe.
When you have an idea of where you might live, use the site www.map-search.ch to see where it is in relation to things and transport links etc.
Very very hard to find an apartment and typically moving dates are just four times a year for most people with the usual contracts - so make sure you have a relocation agent to take you round, even better is is they give you a flat for a month or so, then you can go to viewings once you arrive. Much easier then you can apply straight away.
www.homegate.ch is one of the better known sites for accommodation.
Down side, shops and services as others have said, lots of random paperwork (in German) get DH colleagues here to help. Also many Swiss reserved / lots of rules etc. but Zürich reasonably cosmopolitan.
On the plus side, the working culture here is much more 9-5 than the UK and people rarely have long commutes or traffic problems, so you may be pleasantly surprised at a more present dh ;)
What else can I tell about? Switzerland is a bit of a love it or hate it kind of place, after a year here, you'll know....
It suits me cos I'm organised, like things to run smoothly, am fairly outdoorsy and am not bothered about living somewhere remotely edgy....