Hi...well I am sure this is something to discus with ur mom as to what she feels they will understand....each child is going to be different in how and what u can say....but they need to be informed .
Have a talk with ur MOM...it may help to add that u also r going thru some of the same things, it may help them not be so scared.
i must add that molly knows i have a "boo-boo in my head" and i pretty much co-parent with my mom. so we have been communicating back and forth trying to figure out the best way to tell her. plus my mom knows everything that is going on with me. its just difficult trying to gage how much a 6 year old (she will be 6 jan 3rd) will be able to understand without scaring her
All u can do it continue with the BooBoo in the head ideal and say u know how u feel when ur legs hurt or this happens to u...well that is the same thing that happens to me...we both have BooBoos...
She will put it together is not too young to understand and each child is at a different level, so those around her will know what language is best.