I agree with Exhausted. We have been honest with our girls as they also needed to be prepared for what lays ahead, chemo-radiation, Mri's. There is no easy way to tell them dads got cancer. I hate that we had to tell them that he has brain cancer, but I can only imagine how difficult these last 19months would have been to shelter them from this. Even harder was recently telling them that new tumours are inoperable, but we could not have told them.
Our girls also have lost their dog to cancer last year and their nanie has bowel cancer. Get support for them, CanTeen are great for teens, but for younger there isn't much out there.
Our girls have a great role model in their dad, fighting hard and staing positive.
Good luck,