Oh, mikki, I'm so sorry. I understand how you must feel.
Many years ago we had a 19-year-old Siamese kitty, Porky, who'd been with us since before any of the children were born. He was a feline angel.
When the children came along, Porky took care of them and loved them as if they were his. He let our daughter dress him up in her doll clothes and push him around in her doll baby carriage. He slept with all the children alternately. (There are 5 children, so he made the rounds at night.)
I did in-home daycare at one point and he played with and loved all the children, regardless of how they treated him. He was truly a lover.
When it became apparent that his health was failing and we had to consider saying good-bye, we had a family meeting to make our decision. Everyone agreed that he'd been too good a friend during all our lives to allow him to suffer. I couldn't take him to the vet. Buck did and brought Porky home to be buried.
When we were ready to bury him, Ryan, our youngest, halted the procedure and ran upstairs. He came back down with his prized possession, his R2D2 bath towel, to wrap the kitty in. It still brings tears to my eyes.
I'm sorry you're faced with such a heartbreaking decision, but your pet loves you and you love him enough to take care of him when his life isn't perfect.
Lots of love and hugs are sent your way from our house. Let the tears flow.