How much do you tell your children?

He doesn't need to know about my past. We try to give him information without adding our opinions. He does know vaguely what physical abuse, Emotional abuse, and sexual abuse are.

Things my son (9) knows that we do the following to be better parents:
His parents take meds for bipolar.
His dad go to M******* and mom goes D***** our therapists
His dad goes to group.

Things he knows that he probably shouldn't:
Mom was a bad teen and did drugs. This came from a conversation about about wanting the gold speckles that are in my eyes.
Mom doesn't like eating and dad is overweight.