There are no meetings planned with David before or after the show with the fan club. As his asst said, he doesn't do that. I can only suggest that you get to the venue at around 4pm and wait at the backstage barricade and you might be able to see David drive in for the sound check (I don't know any time but 4pm seems safe if check is anytime between 4and 6pm). You will def get a wave as he gets out of car and goes into stagedoor. It is VERY VERY iffy if he decides to come over to fence to sign - that is his decision at that moment (he did in 2002 for a few), so no way to tell before then. After the show it is really crowded at the fence and no chance that he will come over, never happened at past Westbury shows. All I can do is wish you good luck.
Some club members may be eating at the IHOP down the road from the Music Fair on Jericho Turnpike prior to the show. I gave them that option, if you want to check it out. I will not be at Westbury - not fave venue of mine with back of stage lots of time due to revolving.