You handled that so well Lynn! I just want to share, I think your a fantastic parent from your various posts.
I do recall my mom having a discussion with me about it one time, and how it isn't something to be ashamed of or isnt' wrong, it is just something one does privately and it is a healthy normal thing to do.
I don't recall ever feeling shame, or that masturbation was wrong and I shouldn't be doing it, and I still don't have any feelings of shame, guilt, etc. My mom was very dysfunctional in some ways, but when it comes to having the sex talk I must admitt she did a very good job, and I don't ever feel awkward asking her questions when I have them.
I hope this was some help Lynn,
Best Wishes
Typo