Yes, there are the standards. given the age of your kids, perhaps something that may be interesting for both parents and them would be visiting Ontario Place (
http://www.ontarioplace.com/en/index.html) which is an amusement/entertainment complex on the lake front, relatively close to downtown.
The reason that I mention this place specifically is because the Chinese Lantern festival just opened up there, which will be going on until October and is unique outside of China with being the largest display. This plus the waterpark, the Cinesphere (Omnimax theatre) plus concert forum make it a nice place to be with the family on a summer's day.
Also, depending on your arrival date, the CNE (Canadian National Exhibition) maybe open, which is just across the street. Although my experience has been that this is too tiring to do all in one day, with young kids. (
http://www.theex.com/index.php )
Centre Island is another draw for young families. Access is from the ferry terminal right at the foot of Bay Street. On Centre Island, there is parkland, boardwalk, beaches (one nude one!) a large maze built out of hedges (spruce or boxwood, I'm not sure) which are about 8 ft high, plus Centreville amusement park for kids.
For me, the hightlight has always been the ferry ride over and back. Plus it's a cheap thrill (
www.centreisland.ca ) with a great view of the city. If the day is nice, there are photo ops galor, with multitudes of sail boats.
And of course there's always the CN tower ($$!), Casa Loma (intriguing), the Science Centre (good for kids too), the Beaches Boardwalk and pool (just to chill, and let the kids swim).
There's lots of hotels in the downtown too. The Sheraton is right across the street from the City Hall, so if you ask for a north facing room, you'll get a nice view.