Regulations governing this sort of situation vary from jurisdiction to jurisdiction. It is not uncommon for such circumstances to be kept confidential when the person who behaved inappropriately is not a so-called caretaker of the child. And, as a note of reassurance, in situations such as yours, the interest of child protective services is in help being provided when needed, not in prosecuting or removing children from their homes. I think you'll be fine to arrange a consultation for your son with a
mentalMental retardation
Mental status tests health professional. This will not open up a can of worms, so to speak. As far as your daughter is concerned, your son should apologize to her and assure her he will not repeat this behavior, and you can let her know that he acted inappropriately. Unless you see any worrisome
reactionAllergic reactions
Allergic reactions to medication
Dermatitis, reaction to tinea
Drug allergies
Febrile/cold agglutinins
Insect bite reaction - close-up
Intradermal allergy test reactions
Positive reaction to allergen
Transfusion reaction on her part, you neddn't seek professional help for her. But reiterate with her that it is not permissible for siblings, peers or others to be touching her genital area, and encourage her to let you know if anyone attempts such a thing.
***I know that this was harsh but you folks need to GET REAL.***