If you are raising them for meat, you are probably biting off what you can chew.
How many you get really is up to you. I suggest since it is your first time you don’t go overboard, you can do that once you figure out if it works for you. I don’t know what hatcheries you might buy from in Canada (thanks for posting that information, it changed my answer slightly) but here in the States most hatcheries have a 15 chick or 25 chick minimum, sometimes depending on what time of year they ship. That’s so there are enough of them producing body heat to keep them warm enough when they ship. If you decide to get them from a hatchery, I suggest you get the minimum order. Fifteen is enough to determine whether it works for you. 25 isn’t that bad. If you don’t have those minimums or are getting them from a feed store or somewhere else local, somewhere in that range isn’t bad.
Since you said they are for meat, eggs, and you want to hatch your own, I’d build the facilities a fair amount bigger than the absolute minimum. You will be integrating younger birds and that goes so much easier if they are not shoehorned into a tiny space. I raise mine for your stated goals. My laying/breeding flock is one rooster and 6 to 8 hens but at times I have over 40 chickens, many young and growing to butcher size. Sometimes I have over fifteen hens and pullets laying as I decide which pullets I want to keep and which go into the freezer. Whatever you build you will probably wind up expanding later, such as building a separate grow-out coop and pen, adding a broody buster, maybe a place for a broody to hatch eggs separate to the flock, expanding your roosts in the coop to make integration easier, or something else. Give yourself extra room to add stuff in the main coop and consider that any run you build may be expanded later.
We all have our favorite breeds and all of them are raised in Ontario. Some people will tell you that you can’t raise this breed or that one, yet people do. Some breeds are listed an especially cold hardy though. That normally but not always involves the size of the comb. One risk in truly cold weather is that the chickens can get frostbite on the comb and wattles, especially if you don’t have good ventilation in your coop. While plenty of people raise single combed birds in Canada and Alaska without frostbite problems and without heating the coop, many people suggest a pea combed or rose combed bird. That doesn’t do anything for the wattles but it seems to reduce the chance of frostbite some.
I suggest you go through Henderson’s Breed Chart to look for the breeds that have the qualities you want, then go to Feathersite to see what the birds look like. Two breeds were developed for your purposes especially for colder weather, Buckeyes by a lady in Ohio and Chanteclers by some monks in Canada. You might want to look at those. But really any dual purpose breed can work quite well. You might want to play with these breed selectors too, they might raise a question or two for you to think about.
Henderson’s Breed Chart
There is nothing wrong with either of the breeds you mentioned. I don’t use a breed but instead have a barnyard mix. For eggs, meat, and hatching your own I don’t consider a breed very important. Another possible approach is to get a variety of breeds and see which ones you like best. Eat the ones you don’t like. Most of the time people are happy with whatever they select but occasionally some just don’t like a certain breed for some reason.
There are so many ways you could go about this but mainly don’t go too much overboard on the numbers to start with and build bigger than you think you need.
You might want to follow the link in my signature to get some of my ideas about how much room you need. I’ll give you three articles written by a lady that was in Ontario when she wrote them. They might help you.
Pat’s Cold Coop (winter design) page:
Pat’s Big Ol' Ventilation Page
Pat’s Big Ol' Mud Page (fixing muddy runs):