Yaher koach for distinguishing between peasch preparation and spring cleaning and reminding you congregants that isolated crumbs are not chametz.  However, the shiur of 30 g for a kezayit is machmir when it comes to eating matzah, but it seems quite meikil when it comes to cleaning.  An Oreo cookie, for example is 15g, and we would not call that a crumb too small to eat, I think.  For cleaning wouldn't it be proper to use an olive sized k'zayit?