Hi, I'd like to help you with your question.
If you have any doubts about your husband being safe, either with you or with your children, it is very legitimate for you to leave the marriage now. Anytime you live in fear, it is ok to do what you need to do to feel safe again.
There is no way to tell for sure if your husband is a threat. But if your husband sees nothing wrong with what he did, then there is no guarantee that he won't do this again. And there is no guarantee that he won't come after the children, though that is unlikely since he has not done so already.
To help you and the kids deal with what has happened, you may want to consider counseling. To find a therapist, talk with your doctor about a referral. Or you can search on line at http://therapists.psychologytoday.com/rms/.
I hope this has helped you,
He could be. When someone views and finds child pornography stimulating, the chances that they find real life child abuse acceptable increase, especially when they see nothing wrong with viewing child porn. Many of the people who enjoy child porn also participate so it is feasible that your husband may be abusing a child outside of your family. It is also possible he was abused himself as a child.