how do I tell my children?

Hi everyone,

Last year my mother in law was diagnosed with womb cancer, myself and my husband sat and explained as best we could to our children who were 18, 14 and 9. They were heartbroken, recently we have been told that it has spread to her lungs and that the chemo and radiotherapy hasn't worked and there is talk of her going into a hospice once she cant manage at home.

This is devastating enough but now also my mum has been diagnosed with lung cancer and it has spread to her hip! she will be starting immunotherapy in a week or so. 

Both of these ladies are some of the nicest people you could meet and I'm absolutely heartbroken. How do I tell my children? they know that their Grandma is poorly but not how serious and that she's been getting treatment but they know nothing about their Nanna.

I've never been in this type of situation where I really don't know where to start with what to say for the best, they're good, smart kids and I do want them to know.

Any help is appreciated xxx