You underestimate the ability of children to understand things like this. They tend to not get anxious about health issues like adults do. You could compare your condition to things they understand like, "You know how you don't like a lot of noise when you are tired, that is how Daddy is sometimes." or "You know how when you first wake up, you may not know what is going on, Daddy is like that sometimes." or "Sometimes, Daddy gets really tired and needs it to be quiet."

Kids have far more resilience that we would expect. They see things that we try to hide. They will be much better off if they feel like they are on your team rather than kept in the dark.

My wife was protected from her father's diabetes health conditions and it left her with huge voids and confusion until she was an adult. It was like she was left out of her father's life.

I grew up with my father working in highly classified Top Secret work for the government. We were never told what he did. We always felt left out and didn't understand why my father would get stressed out or may have to work long hours with no explanation.

You kids will grow up with a better and more balanced view of life if they understand. And, you will reduce your stress levels when they crawl up on your lap and just sit quietly. They will feel empowered to help mummy and daddy.