We got a dog when I was a kid, maybe 10 or 11. We (I) loved her, she was an amazing member of the family and will always have a place in my heart. When she got hit by a car, we let her broken leg recover on it's own. She walked with a limp but never stopped smiling. When she got a tumor in her eye, we put her down, and it was really a touching moment. She was given the shot at home, and the whole family traveled in town to be there.
Whatever you do, no matter how much they mean to you, pet's aren't people. Don't try to treat them humanely, they aren't human. Treat them like a pet (there to make you happy, provide a service), care for them, they are important, but you aren't spending money for kin here, you're spending money for what's basically entertainment.