The perfect day out, the Toronto Zoo is wonderful.
There is a lot of parking though some of it is a distance from the zoo itself. On a nice day you will have to queue but there is a clear set of paths you can take. There are places to rest along the way and several places you can get refreshments from. There is a lot of exposed areas here as you would expect from a zoo so take sunscreen.
There are a lot of animals here but there is also a lot of space between them. It won't bee too much for the kids though as I've gone through with them! :-)