How do you fight a following too closely citation in WI where you live when you have IL license??

My son rear ended someone in WI where he lives but still holds an Illinois license. He received a following too close citation. The other party stated they arent goung to court tomorrow, 6/27. He was going to plead not guilty in hope its thrown out. Should the other party go, he was going to ask for a supervision so it doesn't go on his record since he has 2 citations already. One was scheduled to drop off 6/10/18 but the accident happend 5/24 with conviction makes 3. In il 3 can suspend his license. Now we just found out WI doesn't have supervision. Does he still plead not guilty if the other party isnt there and if they are plead guilty and beg for a lesser charge not considered a moving violation??