From someone in WI who went through this, everyone is right. Do NOT give kiddo to GF (visitation cannot be transferred, even to grandparents - thank god). Do you know where ex is going - is it county jail, or the state prison system? That makes a difference IF you are going to take kiddo to visit. If he's going to county jail, then you can go visit during their visiting hours. If you are going to be dealing with state prison system, whole 'nother story. He's going to have to put you and the child on the visiting list, but also, you will have to consent to having kiddo on the list as well. If you are both on the list, he can then call you collect as well (if you want to accept charges and let kiddo talk to him). Not knowing any of your background (how old kiddo is, has he been exercising his visitation, charges, length of sentence, your co-parenting relationship), can't really say much more. Also, I would advise you if he is going into the state prison system, call the corrections dept in Madison and find out his prisoner number and where he's staying (give it a good few months for him to get to the prison destination though - first month or so is just a temp place to see how he's going to do). Get put on the victim's notification list (for when he's released - good stuff to know). Kiddo could write letters to dad and send pix (if you want). Any letters he writes to kiddo will be stamped that they are sent from a corrections facility. Big thing is that you will be responsible for a majority of how kiddo's relationship with dad plays out during this time. You need to make some serious decisions about how this is going to impact kiddo's life, because it will, in more ways than you can imagine, especially if dad is going to be gone for awhile. Again, not knowing some info, I can't really speak to much more.
Hope this helped!