O lovely, I am so sorry to hear that At least he will get to go at home in front of the fire though with his much loved person there to tickle his ears. He is a lucky boy to have been so well loved all these long years and, if that is what is needed, to be allowed to go peacefully to kitty heaven.
See how it goes. It's obvious how you feel about your little man and will do what's best for him but... doesn't make it easier, does it? Huge sympathy.