Goodbye Sir

Tonight I said goodbye to an old friend.
Many years ago my Mom and bro came back from the mall gushing about greyhounds. They wanted one, badly. I thought they meant a bus. I learned they had seen the dogs, ex-racers rescued from the tracks at a booth at the mall. They said they were beautiful dogs. Now, my Mom has always given us everything we wanted if she could, so wanting to do the same I helped her get a greyhound. I volunteered for the organization, made the contacts and we got a tall brindled wonder in exchange. He's actually more like a cat than a dog though. He lies around, loves his bed and his blankets and soaks up all the love he can, with a minimum of movement or personal exertion.
Sure, he's sometimes difficult. He's a 'fraidy dog, won't go down stairs (or up them) and prefers his bed to a walk, but he's so sleek and lovely and quiet and gentle.
Lately, he's been showing his age, increasing incontinence with no warning and trouble breathing, that coupled with my parents going away for three months has led them to schedule him for euthanasia tomorrow.
I just said goodbye.
Personally, I would like a second opinion, as I always do, but I know my requests will be met by anger and upset and ultimately, nothing will change.
I'd take him, I really would, but they won't let me do that either. They say he's too old for a new environment (he's 12) and that having kids with his inability to control himself is not a good combo, but really, my kids make as much mess and poop, does a little more really matter?
I think part of the problem is that I feel guilty. I feel like I shouldn't have taken the steps to get him. If I hadn't, chances are my family wouldn't have either. He would have lived (in my idealized version of his life) with his foster family and other greyhounds until his death at 14 in his sleep on a big pillow next to his playmates. Instead, he lived in a city that scared him, with a family that was rarely home. We should stick to cats, we've never been good at dogs.
So tonight, I cry and feel like hurling because *I* am responsible for 9 years of loneliness, 9 years of fear at motorcycles and trucks passing, 9 years without other greys to run with. I am so so so sorry, dear dog. I wish I could take it all back, every last day, hour and minute, but I can't.
Please forgive me.
Goodbye Sir. I love you.