What do you say to someone at a time like this?
Take your time.
It sounds like God had other plans for your little guy.
The kid has it right ! There is a plan for everything.
My wife had a miscarriage with our first child. It was very tough. I realized that it was not time for our son some several years later after we had our first child. What an incredible joy he was and still is. We talked about having another and I was so scared to be unfair to another child, as I thought I could not love another as much as I loved my first son. That fear was soon put to rest after our second son was born. Wow, what a joy he was and still is today also. I found the love for another child like it was nothing.
It is easy for me to explain that there's a reason for your current loss, and I am sure that you and your wife can't reason it right now. I have faith to believe that you will one day understand why this happened. It may be that you have a son a year or two from now that will amaze the world somehow. It may be that you have another daughter that will bring not only cheer to you and you wife, but be the perfect little sister for your other daughter. Whatever the reason is, you will realize it some day.
I wish you and your family peace through this tough time in life. Your choice to allow him to be an organ donor was a tough choice, I am sure. Maybe you will find comfort with knowledge that your decision to help so many other lives. My oldest will be 17 this month. My wife and I had a talk with him when he was getting his drivers license, as it asks if you want to be an organ donor. This guy had no hesitation, he said "heck yes, they won't do me any good any more". Wow, for a 16 year old to understand and want to help others in so many ways. Both of my sons are incredible and I know why we were delayed in having children. There is a reason why you are delayed now.
Mike