Oh my gosh, you have me in tears reading this. My oldest girl turned 10 a few days ago. I love dogs so much, I've had as many as 6 at a time for the last 45 years. About six months ago, I was in tears when I realized that at my age, I would probably only "know" at most another five dogs in my life.
Just remember the good life you gave Kes and the good life she gave you and your family. You have made the right decision for her. The pain in your heart will recede and be replaced by the joy in your memories.
You'll know the right time to bring in another fuzzy life with loving eyes to help you to celebrate those memories. No dog ever replaces the one before them, they just add to the joy of each dog that has preceded them.
Deb