Tweez,
I don't hike in the ADKs with my Malamute because he's nosy and a wanderer, so I wouldn't make good time with him. But when I take him for walks around home, I realy have to keep a keen eye on his hydration. Being a heavy furred dog, he can get dehydrated easily. So I guess the key is having a hiking breed, and making sure they're hydrated.
I think the hardest part of Seymour would be the slide. But I agree with Rico, dogs have a way of getting around things, They've got that 4-wheel drive with the studded snows. Good luck!
Tom