This.
I had to let my girl go the day I found out last October. She was 11 1/2 and I was getting ready to move across country. I had planned to have a pet service move us and the possibility of having her leg break getting in/out of the car, or just moving around in the car when we were in the middle of nowhere, and knew no vets, made it the only possible decision and simultaneously even more heartbreaking. If you have the opportunity to give him a wonderful, memorable day, then that seems the kindest. I know that I was able to plan my first girl's final day so that everyone she loved best came to see her, she had a last walk in "her" park, and we were both surrounded with love at the last moment. For an experience that stinks, that has been the best by far.