Puppy and Rocked are correct on the who tells the kids. I will be facing this soon, and my W was surprised (to say the least) that I "dumped all of this in HER lap" by telling her SHE would be the one to tell our kids.
Things look dark right now, I know. And, have a good cry. Get it out. Then take a deep breath and pick yourself up. And keep moving forward.
I believe we are never given more than we can handle, even though we think we cannot handle all of it. And, I believe that our true character is shaped, honed and appears in times of adversity. You ARE stronger than this current problem. You may not think you are, but you ARE.