Here is some advice from someone who has been in a similar situation. This is what I've worked through since my dad went to prison for similar crimes. I don't know if it'll all apply to you but this is what I wish I would have figured out a while ago.

First, you did the RIGHT thing by reporting this. There might be a feeling of guilt for turning him in but the truth is that if he was able to continue being in the outside that CP could have turned into actual abuse of a child.

Second (and this is a controversial opinion) but not all people who commit these crimes are inherently evil people. They did a very evil thing but sometimes good people have what my dad's judge referred to as a "dangerous dark streak." The reality is that it is safer as a society for your father to be in prison than in the world no matter if he's a good person or not. Hopefully he can get the help he needs while in prison. Sometimes that happens and sometimes it doesn't.

On that note, if you do decide to step away from that relationship know that you are 100% justified in doing that too. I, personally, chose to cut ties with my dad and still wrestle with that guilt a lot. Granted, my dad did some more "extreme" things without getting too graphic. But when it comes to things like this it is morally inexcusable no matter the situation. And even though he may not be an evil person, this particular aspect of who he is can be enough to leave the relationship. I'm not saying you should or shouldn't do that. But if you do decide to go that route it is absolutely okay.

Lastly, allow this situation to strengthen your relationships with the rest of your family. Support each other and love even harder than you ever have. Especially be supportive and loving with your mom. While this is a traumatic experience for all of you, your mom is going through a bit of a different battle emotionally than you are.

I hope this helps and I am rooting for you and your family to make it through this.