FWIW, there was a marathon both of us were scheduled to run in a couple weeks ago and WAH didn't go. I totally expected him to be there and totally relieved he didn't. But, just surround yourself with friends and just treat him as you would any other person... polite but be indifferent.
Hope you have a good time!
M40, H39 M17 T20 D13, S12 H moved out 05/09 D filed 1/10