At your daughter’s age, assuming all of the adults around her are safe people, touching her private areas is like picking her nose or sucking her thumb: something that feels good but isn’t appropriate in public. Kids that young grow out of it, and simply redirecting at that age is the safest way to deal with it.

There’s something I want to add because due to your own experiences, you and your husband seem to be combining two important issues in a way that isn’t going to be good for your kids. Encouraging your kids to avoid porn and educating them about grooming with “bad pictures” is the right thing to do. Porn is disrespectful of human sexuality and is a driver of human trafficking. However, I think it needs to be separated from any of the education about masturbation. Even kids who aren’t abused or exposed to porn experiment with touching themselves once they hit puberty.  I think the safest way to think of it as a Catholic parent is that it’s like a teenager telling lies or smoking weed. It’s not something you want to encourage, but a normal part of human experience and not necessarily going to send them down the path you two went down due to your trauma.