Mike, there's not much anyone can say to make you or Kareem's family feel any better. There just are no words. The thing that you have to be grateful for is that for the past seventeen years, you have been a loyal friend to Kareem and he to you. That's already a lot. He'll have my thoughts for sure.
As for little Riley, she is starting a great journey that will make you proud all of your life. Cherish these moments as I know that that alone takes some of the stress away from thinking of Kareem.
Be well.