Yes we did have a good time - but tbh it felt a bit like work occasionally!
We did Toronto, Niagara, Whistler, Vancouver and Seattle in 14 days. I packed and unpacked 5 times, and we twice had to adjust to different time zones (Toronto 5 hours different to UK, and Vancouver another 3 hours difference on top). We had 1 internal flight, and three 2-3 hour car transfers including one delayed border crossing between Canada and the US.
We have some good memories and did some great stuff (black bear eco tour around Whistler etc) but I did make my feelings plain to dh once or twice when dc's were incredibly over-tired and over-stimulated!(My fault for not getting more involved at the holiday planning stage)
Next year we are doing Venice for 4 nights followed by a sumptuous Italian villa by the sea for a week or so. Somewhat simpler and more relaxing!
We didn't manage all of your recommendations but included the majority of them, so
Toronto: CN tower, Toronto islands and brilliant Museum whose name escapes me (it's late and I'm tired!) with fab natural history bit
Niagara: self explanatory
Whistler: Black bear tour, pony trekking
Vancouver: The childrens science museum, Stanley Park, and Grouse Mountain (with 'world famous' lumber jack show - phwoar)
Seattle: The Space Needle, Sci-fi museum, acquarium, harbour tour and the dc loved the sky train monorail to Seattle Centre...
etc
Have any of you got holidays coming up soon?