My fiancé and I have decided to allow children of immediate family only to attend our wedding.  This will keep the count fairly low, as it is a formal plated dinner and we want to make sure it doesn't sound like a McDonalds Playplace in our somewhat intimate reception venue. 
 We invited my fiancées cousin with HER NAME AND HER BOYFRIENDS NAME ONLY.  She sent her reply back with 3 people on it to include her boyfriends son.  He is 2 1/2, and at a wedding a few weeks ago he screamed, cried, and ran around crazy the whole time.  This child is not a member our family and we have only met him once a couple weeks ago.  We have put so much time and effort into planning a beautiful party for our guests.  How do I tell them that he is not welcome without causing drama?  ANY SUGGESTIONS WOULD BE AWESOME.