How much do you share with grandkids or your children?

When I was diagnosed my granddaughter was 3 so no issue of discussions. She is now a very inquisitive 5 1/2 year old. I have shared with her that I had an MRI and infusion . . . because she had to have a MRI earlier this year and is on her 6th IVIG infusion (5 hr long).
She wanted to know why I was quarantining during recent Halloween and didn’t trick or treat with her and her little brother (they are sick often with daycare and school viruses/colds). She was satisfied with the answer that I’m going to the hospital and they’ll send me home if I’m sick. To her, the hospital is where you go for infusions and scans so no real concern about more intensive procedures (I have surgery tomorrow).
But I know she will ask more questions. How much is too much?
I don’t mind sharing about my condition- most everyone I know are aware. But I don’t want to scare her. I’m okay with giving a non-answer to her questions . . . but then don’t want her to later think I lied.
What to do?