HELP!!!! Need a good excuse to cancel weekend plans with my b/f....?

just tell him you're going with your ex to the cookout because its something for your son to see the 3 together again, thats something that your current b/f has to accept, and that is that you need to stay in friendship closeness with your ex for your son's sake.... he has to understand that you will always have a connection with your ex and ask to make plans on sunday or another day.. dont sound sorry or that will put you in the guilty section!!