I don’t know about the shedding, and I’m not a dog owner, but the Golden Retriever who lives on my block is the most laid-back dog I’ve ever seen. I really like him - his owners let him hang out in the front yard without a leash or a fence, and I walk by him on my way to school. I say “hi”, he looks at me and goes back to whatever it is he’s doing - usually watching squirrels. I can’t imagine that he gets flustered by kids.
We looked into Giant Schnauzers as well, but decided on the Standard, mostly because Giants really are big, big dogs and we felt it wouldn’t make sense if, in a family of seven, only three people were big enough to control the animal while out on walks (at the time…now, of course, three of my four brothers are taller than me and outweigh me). They are generally very goofy as young dogs, but tend to become sharper as adults.
I’d recommend finding some bull mastiff mailing lists. Not only will you learn tons on the breed but you’ll also start ‘meeting’ breeders, hopefully some in your area that will invite you over to get some mastiff experiences. Once you build up some rapport with a breeder you feel comfortable with, you may qualify to adopt one of their retired show dogs (most likely fixed before placing.)
You can also check out the breed-specific rescues. I’m sure you’ll find some older dogs there too!
http://bullmastiff.us/rescue/index.html
http://www.bullmastiff.org/list.htm ~ Mailing list
So did we–I like every single thing about them except the suggestion by a lot of folks that they’re notorious barkers. I think our current dog has barked fewer than five times in his entire life, and it’s one of my favorite things about him 
Goldens are awesome, but if allergies are involved, I don’t think they’re a good choice. My second favorite dog in the universe (as opposed to the yellow lab who is my favorite dog in the universe) is a redheaded Golden, but if he’s not brushed…oy. But he loooooooves to be brushed. I’d still worry about dander and such unless he was being bathed at least weekly.
I’ve met several really great poodles. (I’m talking Standards, not tiny useless things.) The only coat-concerned downside that I’m aware of is the grooming; you really do have to get them haircuts, even if you just do a basic puppy cut sort of haircut. And having brushed out a poodle or two that doesn’t get groomed often enough…please, please, please, please get your poodle groomed more than a couple of times a year.
That is an awesome picture!
They do fine in Florida. My neighbor’s got one. She’s amazingly, awesomely terrific. 
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Thanks. Sadly, we lost Riley (the dog) to Lymphoma 2 months ago. 