Poor guy, that will be tough fo rhim to deal with, I pray that he recovers well and soon!
For you I think you have a good deal of work in store to support him, by supporting your kids. You already mentioned the 15 yr old and the issues there, so now will be time for you the Mother to be the Rock for the kids. This will help the Father to not worry more than he already will have to.
Why are you sad? Cancer is as much a part of this life as anything else, it's all around us and 1 in 10 will get it in their lifetime.
Instead of being "sad" for yourself or the kids, you need to get on board with the local Cancer Society efforts, get involved with your kids...teach them, yourself and your EX to say, "**** Cancer!!"
This is a wonderful oppurtunity to show strength, to contribute for a cause that has no end in sight. Your kids, yourself and your EX are now in a battle that is waged everyday around the world...but the war is being won!
Take heart!! Sieze the day to rally for your EX and muster the strength of others in your friends and family, the community to offer your EX and your kids the BEST possible way to deal with this...FIGHT BACK!
Your local Cancer Society has ALL the resources you need to make this a successful campaign, and along the way you will meet the strongest and most fearlessly dedicated people you will have ever met. This will leave a permanent impression upon your children and should give you the satisfaction of knowing that you did the right thing when your time to serve the fight came.
My Father passed before my eyes, his battle lost in only 3 months, but I fight on for ALL the Father's, Mother's , Brothers and Sisters...Fight for the Cure. Start today!
Relay For Life