Summer holiday flying in/out Toronto from London

Hi all, I am planning a Canadian holiday this summer, last week of July for 2 weeks and 2 days. Myself (dad) and my three daughters, 20yr, 18yr and 12yr. We fly from London to Toronto and return via Toronto. I'll hire a car for when we leave Toronto. My itinerary so far is:

Toronto - 3 days (including day trip to Niagara falls).

Algonquin Park - 3 days.

Mont Tremblant - overnight stop to break up the journey.

Saguenay - 4 nights.

Quebec city - 2 nights.

Montreal - 3 nights (or maybe 2 and 1 more in Toronto?).

Back to Toronto.

We've never been to Canada before and would appreciate some feedback on our itinerary.

We are not huge outdoorsy active people but will swim, canoe, short hike, and I love doing a bbq etc. We'd like to see a mix of city and more remote areas. I am not sure where to stay in Saguenay, any suggestions please. And is 3 nights in Montreal too much? Would 3 nights in Quebec be better or another night in Toronto?