Hi! I know this post is old but I'm new here and would appreciate some info of your experience on flying with pet(s)! I'm planning to fly my pets with me from the Philippines, too
I can share my experience flying inside Canada with my 2 pets. I know it's not exactly your situation, but I doubt you will find anyone who brought more than 2-3 pets into the country with them.
If you have any small pets, they will generally not do well in cargo hold. It gets very cold and only bigger animals are able to handle that situation well. There are plenty of stories out there about smaller pets dying in cargo because of the environment and how stressful it is. The airlines are never liable for your pet's well-being. If you choose to have them in the cabin with you, they have to be small enough to fit into a carrier comfortably and will have to stay in it for the duration of the flight. The carrier has to fit under the seat in front of you, so I recommend a soft shell carrier that can bend a little.
From my experience flying on Air Canada, there are only 2 pets permitted inside the cabin on each flight, so you will have to make arrangements beforehand & also pay for their tickets ($50-100 per pet) to make sure nobody else has taken those spots up. Again, I don't know about international flights, but I doubt it's much different.
When you get to Canada, you will have to present all of their vaccination records, etc to an inspector (so you will definitely be going through secondary) while he checks on each pet.
Flying with 2 pets with my husband inside Canada was tough. I cannot imagine flying with 8, as well as having to go through inspection and then trying to find a landlord in Canada who will be fine with all of those animals on their property (doubt it's legal, but maybe you can find a big house to rent with a backyard). Good luck!!