If you're renting a car, Niagara Falls is only an hour away, the Great Wolf Lodge there is fantasic!! We just returned from a trip there. My son will be three in August and he absolutely loved it!!! I would personally do Great wolf over Canada's Wonderland, but thats just my opinion
I have to agree. The Great Wolf Lodge is fantastic, and would translate into a much more memorable (and far more relaxing) vacation than Canada's Wonderland. Plus, there's TONS of stuff for families to do in Niagara Falls (if you're thinking themepark, Marineland is great

).
If you're really stuck on Toronto (which is tons of fun too....we're headed there for a week in August), here's a few ideas for young kiddos:
- Ontario Place
- Fantasy Fair (its an indoor amusement park inside the Woodbine Centre shopping mall)
- Bowmanville Zoo (is outside the city of Toronto, but would be a better choice, IMHO, than the Toronto Zoo for smaller children)
- Toronto Zoo
- Ontario Science Centre
- Wild Water Kingdom (in Brampton)
Also, check out the Todays Parent Kidsummer program at
http://www.kidsummer.com/
They have some great "kid-friendly" activities happening across the Greater Toronto Region thoughout the summer. Some are free, some may only require that you pay adult admission. Might give you some ideas that you hadn't considered before!
Also, check out:
www.toronto4kids.com
This is a great resource for ideas on fun things to do in Toronto! Click on "Kid's Directory", then "Fun Things to Do". The list is broken down into sub-lists (like "amusement parks", "indoor playgrounds", "waterparks", "petting zoos", etc.).
Have an awesome trip!!
