Here's my two cents, and before I begin I'll say for sure not a Malinois for you and your family. With that being said here is a list of breeds that I'd suggest would fit your criteria. 

Leavitt Olde Bulldogs 

American Bulldog 

Cane Corso

Rottweiler

Presa Canario 

Bull Mastiff

Dogue de Bourdeaux

Rhodesian Ridgeback 

In the list of breeds that I'd suggest, they would all be wonderful pets for children and fit your criteria for temperament, but with that all being said the Corso and Rottweilers would be on the bottom of my list when it comes to young children but your kids are (5 & 7) of age and they can learn to be respectful to the dogs so that shouldn't be a big deterrent in not taking those breeds serious. In any event I'd take the time to find the most out-going and leveled tempered dog all the while socializing it early and often. 

You didn't go into "details" into how you'd shelter your dog (indoor/outdoor) in home or a well weathered kennel? Aside from the Bourdeaux and Rottweiler, all the breeds mentioned are short haired, usually meaning "low shedding" but depending those "details" they'd all do well in Toronto weather. Just remember, they aren't Saint Bernard's or CAO's. 

Aside from the Rhodesian, Bull Mastiff and DDB those other breeds would excel in advance obedience work and "bite work" not to say that the three above wouldn't. It's more "the exception to the rule" but basic/above basic training and you'll be fine with any of the breeds.

All in all, the breeds i suggest can all be "nice and calm family dog that will tolerate strangers but will protect if push comes to shove" just keep in mind that finding the right puppy, firm and moderate training and follow through from you the owner to see these goals through is important to having the dog you want. It definitely isn't just buying one of these breeds. 

"A breeder is going to tell you everything you want to hear, cause he wants to make a sale"

My name is Steve the dog trainer based in Los Angeles Ca. I've trained and owned every breed I mentioned. I've titled AB's in Schutzhund and specialize in protection training. 

Best regards