Just got back after spending a couple of hours with the little one (17mth old) its really good (just get their early if you want to park)

http://www.roggenhausen.ch/

Anyone else got any good tips for Aargau / Zurich for little ones?

The Tierpark in Goldau is quite nice but a few hills, you can buy boxes of food and hand feed the deer! Its also nice becasue you can combine it with the train from Arth Goldau to the top of Mt. Rigi, makes a very nice day outing.

http://www.tierpark.ch/

I also like Wildnispark, all sorts of animals some very close and a grill, you can drive or take a train very clsoe to Zurich.

http://www.wildnispark.ch/