Frannie72
Please understand that none of here are doctors; on this site you can bounce ideas off others, and hear how others dealt with issues. You may receive a range of opinion, and only you (perhaps with qualified local help) have to find your own way.
My children were older than yours at time of my cancer diagnosis.Once I had an idea of the path ahead (with much help from this site) I wrote a letter to my children, including the one (also an adult) still living at home, concisely stated, I said, " I have cancer, I am receiving treatment, and there is no urgency to my situation. I will let you know if that changes."
Of course the kids were concerned, and suddenly there were many more visits to "the folks" than normal. Once the kids were over the shock, life settled down. Being truthful, but not providing extreme detail, worked for me.
The grands know that grandpa is sick sometimes. When my immune system is down, the grands just need to be told once (or 3 times) why gramps is wearing that funny germ mask, and that he will not be giving or taking any hugging and cuddling on this visit. They will, sooner or later, associate the word cancer - perhaps it will be a bit less scary to to them.
Almost four years ago, on this site, I was told "Cancer is a team sport" - it involves and affects the patient and those around him/her. I have found that to be true.
We each have to work our own way through this disease.
Best,
Jack