You could say this - None of us are perfect. We all make mistakes, and sometimes, we make bad choices. Sometimes those choices mean we have to go to jail, and sometimes we have to go for a very long time.
Unfortunately, Daddy did this. That doesn't mean that he doesn't love you. It just means that he made some bad choices. That doesn't mean that we have to stop loving him. But it does mean that he has to go away. It's ok if you miss him, and it's ok for you to be angry at him, but it's also ok to still love him - you can even still love him while you're sad and mad! Daddy and I both understand this, and we both love you very much. You can write letters, visit, talk on the phone, send him care packages, etc (suggest to them whatever it is that you can do). But, if you don't feel like it, that's ok, too. You don't have to do these things. No matter what you decide, nothing is going to stop us from loving you.
at 6:55 AM on Apr. 5, 2010