Nel, If you normally go to the tournaments w/your D17, then go. Nothing says you have to sit w/him and his mother, nor do you have to share a meal w/them...if they invite you to do things, then you will need to decide then whether or not to accept...but your D17 stills needs your support and I certainly wouldn't let their attendance stand in your way of going.
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.
