Julie, If you don't set the story straight about this step sister business...who will? They aren't married, therefore there's no relationship there by way of marriage.
As for the game this weekend...go and have fun. It's your son's game and whatever those two loony birds do, ignore them. If you see them, sit somewhere else and focus on the game. If you happen to run into them, stay calm. The more you react to them, the more justification that they have for what they are doing and you don't want the public to see a drama play out in front of them. Be the classy lady that I know you are. Think of it as a star performance on stage and do your best at being civil. Nothing more.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
